Analysis of laser remote fusion cutting based on a mathematical model

NASA Astrophysics Data System (ADS)

Matti, R. S.; Ilar, T.; Kaplan, A. F. H.

2013-12-01

Laser remote fusion cutting is analyzed by the aid of a semi-analytical mathematical model of the processing front. By local calculation of the energy balance between the absorbed laser beam and the heat losses, the three-dimensional vaporization front can be calculated. Based on an empirical model for the melt flow field, from a mass balance, the melt film and the melting front can be derived, however only in a simplified manner and for quasi-steady state conditions. Front waviness and multiple reflections are not modelled. The model enables to compare the similarities, differences, and limits between laser remote fusion cutting, laser remote ablation cutting, and even laser keyhole welding. In contrast to the upper part of the vaporization front, the major part only slightly varies with respect to heat flux, laser power density, absorptivity, and angle of front inclination. Statistical analysis shows that for high cutting speed, the domains of high laser power density contribute much more to the formation of the front than for low speed. The semi-analytical modelling approach offers flexibility to simplify part of the process physics while, for example, sophisticated modelling of the complex focused fibre-guided laser beam is taken into account to enable deeper analysis of the beam interaction. Mechanisms like recast layer generation, absorptivity at a wavy processing front, and melt film formation are studied too.

Direct-laser metal writing of surface acoustic wave transducers for integrated-optic spatial light modulators in lithium niobate

NASA Astrophysics Data System (ADS)

Datta, Bianca C.; Savidis, Nickolaos; Moebius, Michael; Jolly, Sundeep; Mazur, Eric; Bove, V. Michael

2017-02-01

Recently, the fabrication of high-resolution silver nanostructures using a femtosecond laser-based direct write process in a gelatin matrix was reported. The application of direct metal writing towards feature development has also been explored with direct metal fusion, in which metal is fused onto the surface of the substrate via a femtosecond laser process. In this paper, we present a comparative study of gelatin matrix and metal fusion approaches for directly laser-written fabrication of surface acoustic wave transducers on a lithium niobate substrate for application in integrated optic spatial light modulators.

Proposal for a novel type of small scale aneutronic fusion reactor

NASA Astrophysics Data System (ADS)

Gruenwald, J.

2017-02-01

The aim of this work is to propose a novel scheme for a small scale aneutronic fusion reactor. This new reactor type makes use of the advantages of combining laser driven plasma acceleration and electrostatic confinement fusion. An intense laser beam is used to create a lithium-proton plasma with high density, which is then collimated and focused into the centre of the fusion reaction chamber. The basic concept presented here is based on the 7Li-proton fusion reaction. However, the physical and technological fundamentals may generally as well be applied to 11B-proton fusion. The former fusion reaction path offers higher energy yields while the latter has larger fusion cross sections. Within this paper a technological realisation of such a fusion device, which allows a steady state operation with highly energetic, well collimated ion beam, is presented. It will be demonstrated that the energetic break even can be reached with this device by using a combination of already existing technologies.

High-energy krypton fluoride lasers for inertial fusion.

PubMed

Obenschain, Stephen; Lehmberg, Robert; Kehne, David; Hegeler, Frank; Wolford, Matthew; Sethian, John; Weaver, James; Karasik, Max

2015-11-01

Laser fusion researchers have realized since the 1970s that the deep UV light from excimer lasers would be an advantage as a driver for robust high-performance capsule implosions for inertial confinement fusion (ICF). Most of this research has centered on the krypton-fluoride (KrF) laser. In this article we review the advantages of the KrF laser for direct-drive ICF, the history of high-energy KrF laser development, and the present state of the art and describe a development path to the performance needed for laser fusion and its energy application. We include descriptions of the architecture and performance of the multi-kilojoule Nike KrF laser-target facility and the 700 J Electra high-repetition-rate KrF laser that were developed at the U.S. Naval Research Laboratory. Nike and Electra are the most advanced KrF lasers for inertial fusion research and energy applications.

Analysis of laser remote fusion cutting based on a mathematical model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matti, R. S.; Department of Mechanical Engineering, College of Engineering, University of Mosul, Mosul; Ilar, T.

Laser remote fusion cutting is analyzed by the aid of a semi-analytical mathematical model of the processing front. By local calculation of the energy balance between the absorbed laser beam and the heat losses, the three-dimensional vaporization front can be calculated. Based on an empirical model for the melt flow field, from a mass balance, the melt film and the melting front can be derived, however only in a simplified manner and for quasi-steady state conditions. Front waviness and multiple reflections are not modelled. The model enables to compare the similarities, differences, and limits between laser remote fusion cutting, lasermore » remote ablation cutting, and even laser keyhole welding. In contrast to the upper part of the vaporization front, the major part only slightly varies with respect to heat flux, laser power density, absorptivity, and angle of front inclination. Statistical analysis shows that for high cutting speed, the domains of high laser power density contribute much more to the formation of the front than for low speed. The semi-analytical modelling approach offers flexibility to simplify part of the process physics while, for example, sophisticated modelling of the complex focused fibre-guided laser beam is taken into account to enable deeper analysis of the beam interaction. Mechanisms like recast layer generation, absorptivity at a wavy processing front, and melt film formation are studied too.« less

Laser-induced fusion of human embryonic stem cells with optical tweezers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen Shuxun; Wang Xiaolin; Sun Dong

2013-07-15

We report a study on the laser-induced fusion of human embryonic stem cells (hESCs) at the single-cell level. Cells were manipulated by optical tweezers and fused under irradiation with pulsed UV laser at 355 nm. Successful fusion was indicated by green fluorescence protein transfer. The influence of laser pulse energy on the fusion efficiency was investigated. The fused products were viable as gauged by live cell staining. Successful fusion of hESCs with somatic cells was also demonstrated. The reported fusion outcome may facilitate studies of cell differentiation, maturation, and reprogramming.

Efficient neutron generation from solid-nanoparticle explosions driven by DPSSL-pumped high-repetition rate femtosecond laser pulse

NASA Astrophysics Data System (ADS)

Watari, T.; Matsukado, K.; Sekine, T.; Takeuchi, Y.; Hatano, Y.; Yoshimura, R.; Satoh, N.; Nishihara, K.; Takagi, M.; Kawashima, T.

2016-03-01

We propose novel neutron source using high-intensity laser based on the cluster fusion scheme. We developed DPSSL-pumped high-repetition-rate 20-TW laser system and solid nanoparticle target for neutron generation demonstration. In our neutron generation experiment, high-energy deuterons were generated from coulomb explosion of CD solid- nanoparticles and neutrons were generated by DD fusion reaction. Efficient and stable neutron generation was obtained by irradiating an intense femtosecond laser pulse of >2×1018 W/cm2. A yield of ∼105 neutrons per shot was stably observed during 0.1-1 Hz continuous operation.

New amplifying laser concept for inertial fusion driver

NASA Astrophysics Data System (ADS)

Mourou, G. A.; Labaune, C.; Hulin, D.; Galvanauskas, A.

2008-05-01

This paper presents a new amplifying laser concept designed to produce high energy in either short or long pulses using coherent or incoherent addition of few millions fibers. These are called respectively CAN for Coherent Amplification Network and FAN for Fiber Amplification Network. The fibers would be large core or Large Mode Area (LMA) which have demonstrated up to 10, mJ output energy per fiber1. Such a system could meet the driver criteria of Inertial Fusion Energy (IFE) power plants based on Inertial Confinement Fusion (ICF), in particular high efficiency and high repetition rate.

Remarks to SBS PCM based self-navigation of laser drivers

NASA Astrophysics Data System (ADS)

Kalal, M.; Matena, L.; Kong, HJ; Martinkova, M.; Cha, S.

2016-03-01

A novel technology of self-navigation of laser drivers on injected inertial fusion energy pellets employing phase conjugating mirrors based on stimulating Brillouin scattering was recently proposed. Its feasibility as well as various implications were gradually studied and working solutions to potential problems were always suggested. As this technology could help to overcome several burning key issues of inertial fusion (e.g., a sufficiently precise navigation of laser drivers on injected pellets in the case of a direct drive scheme and decreased requirements on high-repetition high-power lasers) it gradually started to attract a carefully measured tentative interest among the major inertial fusion oriented laboratories and projects. In this paper the next step in this research path will be reported. It concerns the resulting phase and amplitude structures created by multiple low energy drivers (glints) illuminating the pellet during the first stage of the process after their reflection and a subsequent superposition on the collecting/focusing final optics. It was demonstrated that with a large number of such drivers acting simultaneously from many angles the situation gets somewhat complicated and requires more detailed studies/suggestions of suitable configurations.

Hybrid indirect-drive/direct-drive target for inertial confinement fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Perkins, Lindsay John

A hybrid indirect-drive/direct drive for inertial confinement fusion utilizing laser beams from a first direction and laser beams from a second direction including a central fusion fuel component; a first portion of a shell surrounding said central fusion fuel component, said first portion of a shell having a first thickness; a second portion of a shell surrounding said fusion fuel component, said second portion of a shell having a second thickness that is greater than said thickness of said first portion of a shell; and a hohlraum containing at least a portion of said fusion fuel component and at leastmore » a portion of said first portion of a shell; wherein said hohlraum is in a position relative to said first laser beam and to receive said first laser beam and produce X-rays that are directed to said first portion of a shell and said fusion fuel component; and wherein said fusion fuel component and said second portion of a shell are in a position relative to said second laser beam such that said second portion of a shell and said fusion fuel component receive said second laser beam.« less

Effect of tapered magnetic field on expanding laser-produced plasma for heavy-ion inertial fusion

DOE PAGES

Kanesue, Takeshi; Ikeda, Shunsuke

2016-12-20

A laser ion source is a promising candidate as an ion source for heavy ion inertial fusion (HIF), where a pulsed ultra-intense and low-charged heavy ion beam is required. It is a key development for a laser ion source to transport laser-produced plasma with a magnetic field to achieve a high current beam. The effect of a tapered magnetic field on laser produced plasma is demonstrated by comparing the results with a straight solenoid magnet. The magnetic field of interest is a wider aperture on a target side and narrower aperture on an extraction side. Furthermore, based on the experimentallymore » obtained results, the performance of a scaled laser ion source for HIF was estimated.« less

Records for conversion of laser energy to nuclear energy in exploding nanostructures

NASA Astrophysics Data System (ADS)

Jortner, Joshua; Last, Isidore

2017-09-01

Table-top nuclear fusion reactions in the chemical physics laboratory can be driven by high-energy dynamics of Coulomb exploding, multicharged, deuterium containing nanostructures generated by ultraintense, femtosecond, near-infrared laser pulses. Theoretical-computational studies of table-top laser-driven nuclear fusion of high-energy (up to 15 MeV) deuterons with 7Li, 6Li and D nuclei demonstrate the attainment of high fusion yields within a source-target reaction design, which constitutes the highest table-top fusion efficiencies obtained up to date. The conversion efficiency of laser energy to nuclear energy (0.1-1.0%) for table-top fusion is comparable to that for DT fusion currently accomplished for 'big science' inertial fusion setups.

Development of Electron Beam Pumped KrF Lasers for Fusion Energy

DTIC Science & Technology

2008-01-01

Direct drive with krypton fluoride (KrF) lasers is an attractive approach to inertial fusion energy (IFE): KrF lasers have outstanding beam spatial...attractive power plant [3]. In view of these advances, several world-wide programs are underway to develop KrF lasers for fusion energy . These include

Parameter space for the collective laser coupling in the laser fusion driver based on the concept of fiber amplification network.

PubMed

Huang, Zhihua; Lin, Honghuan; Xu, Dangpeng; Li, Mingzhong; Wang, Jianjun; Deng, Ying; Zhang, Rui; Zhang, Yongliang; Tian, Xiaocheng; Wei, Xiaofeng

2013-07-15

Collective laser coupling of the fiber array in the inertial confinement fusion (ICF) laser driver based on the concept of fiber amplification network (FAN) is researched. The feasible parameter space is given for laser coupling of the fundamental, second and third harmonic waves by neglecting the influence of the frequency conversion on the beam quality under the assumption of beam quality factor conservation. Third harmonic laser coupling is preferred due to its lower output energy requirement from a single fiber amplifier. For coplanar fiber array, the energy requirement is around 0.4 J with an effective mode field diameter of around 500 μm while maintaining the fundamental mode operation which is more than one order of magnitude higher than what can be achieved with state-of-the-art technology. Novel waveguide structure needs to be developed to enlarge the fundamental mode size while mitigating the catastrophic self-focusing effect.

Recent advances and challenges for diode-pumped solid-state lasers as an inertial fusion energy driver candidate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Payne, S.A.; Beach, R.J.; Bibeau, C.

We discuss how solid-state laser technology can serve in the interests of fusion energy beyond the goals of the National Ignition Facility (NIF), which is now being constructed to ignite a deuterium-tritium target to fusion conditions in the laboratory for the first time. We think that advanced solid-state laser technology can offer the repetition-rate and efficiency needed to drive a fusion power plant, in contrast to the single-shot character of NIF. As discuss below, we propose that a gas-cooled, diode-pumped Yb:S-FAP laser can provide a new paradigm for fusion laser technology leading into the next century.

An overview of the development of the first wall and other principal components of a laser fusion power plant

NASA Astrophysics Data System (ADS)

Sethian, John D.; Raffray, A. Rene; Latkowski, Jeffery; Blanchard, James P.; Snead, Lance; Renk, Timothy J.; Sharafat, Shahram

2005-12-01

This paper introduces the JNM Special Issue on the development of a first wall for the reaction chamber in a laser fusion power plant. In this approach to fusion energy a spherical target is injected into a large chamber and heated to fusion burn by an array of lasers. The target emissions are absorbed by the wall and encapsulating blanket, and the resulting heat converted into electricity. The bulk of the energy deposited in the first wall is in the form of X-rays (1.0-100 keV) and ions (0.1-4 MeV). In order to have a practical power plant, the first wall must be resistant to these emissions and suffer virtually no erosion on each shot. A wall candidate based on tungsten armor bonded to a low activation ferritic steel substrate has been chosen as the initial system to be studied. The choice was based on the vast experience with these materials in a nuclear environment and the ability to address most of the key remaining issues with existing facilities. This overview paper is divided into three parts. The first part summarizes the current state of the development of laser fusion energy. The second part introduces the tungsten armored ferritic steel concept, the three critical development issues (thermo-mechanical fatigue, helium retention, and bonding) and the research to address them. Based on progress to date the latter two appear to be resolvable, but the former remains a challenge. Complete details are presented in the companion papers in this JNM Special Issue. The third part discusses other factors that must be considered in the design of the first wall, including compatibility with blanket concepts, radiological concerns, and structural considerations.

Ignition and Inertial Confinement Fusion at The National Ignition Facility

NASA Astrophysics Data System (ADS)

Moses, Edward I.

2016-10-01

The National Ignition Facility (NIF), the world's largest and most powerful laser system for inertial confinement fusion (ICF) and for studying high-energy-density (HED) science, is now operational at Lawrence Livermore National Laboratory (LLNL). The NIF is now conducting experiments to commission the laser drive, the hohlraum and the capsule and to develop the infrastructure needed to begin the first ignition experiments in FY 2010. Demonstration of ignition and thermonuclear bum in the laboratory is a major NIF goal. NIF will achieve this by concentrating the energy from the 192 beams into a mm3-sized target and igniting a deuterium-tritium mix, liberating more energy than is required to initiate the fusion reaction. NIP's ignition program is a national effort managed via the National Ignition Campaign (NIC). The NIC has two major goals: execution of DT ignition experiments starting in FY20l0 with the goal of demonstrating ignition and a reliable, repeatable ignition platform by the conclusion of the NIC at the end of FY2012. The NIC will also develop the infrastructure and the processes required to operate NIF as a national user facility. The achievement of ignition at NIF will demonstrate the scientific feasibility of ICF and focus worldwide attention on laser fusion as a viable energy option. A laser fusion-based energy concept that builds on NIF, known as LIFE (Laser Inertial Fusion Energy), is currently under development. LIFE is inherently safe and can provide a global carbon-free energy generation solution in the 21st century. This paper describes recent progress on NIF, NIC, and the LIFE concept.

Numerically Simulating Collisions of Plastic and Foam Laser-Driven Foils

NASA Astrophysics Data System (ADS)

Zalesak, S. T.; Velikovich, A. L.; Schmitt, A. J.; Aglitskiy, Y.; Metzler, N.

2007-11-01

Interest in experiments on colliding planar foils has recently been stimulated by (a) the Impact Fast Ignition approach to laser fusion [1], and (b) the approach to a high-repetition rate ignition facility based on direct drive with the KrF laser [2]. Simulating the evolution of perturbations to such foils can be a numerical challenge, especially if the initial perturbation amplitudes are small. We discuss the numerical issues involved in such simulations, describe their benchmarking against recently-developed analytic results, and present simulations of such experiments on NRL's Nike laser. [1] M. Murakami et al., Nucl. Fusion 46, 99 (2006) [2] S. P. Obenschain et al., Phys. Plasmas 13, 056320 (2006).

Laser-Driven Fusion.

ERIC Educational Resources Information Center

Gibson, A. F.

1980-01-01

Discusses the present status and future prospects of laser-driven fusion. Current research (which is classified under three main headings: laser-matter interaction processes, compression, and laser development) is also presented. (HM)

The Electra KRF Laser System

DTIC Science & Technology

2007-06-01

the Naval Research Laboratory used to advance the technology towards a KrF laser driver for inertial fusion energy [1-7]. Electra consists of two e...krypton fluoride lasers for fusion energy ," Proc. IEEE, vol. 92, pp. 1043-1056, July 2004. [2] M. C. Myers, J. D. Sethian, J. L. Giuliani, R. Lehmberg...KrF lasers for inertial fusion energy ," Nucl. Fusion, vol. 44, pp. S247-S253, Nov. 2004. [3] J. D. Sethian, M. Friedman, R. H. Lehmberg, M. Myers

Thermal Loading of Thin Metal Foils Used as Electron Beam Windows for a KRF Laser

DTIC Science & Technology

2005-06-01

the Inertial Fusion Energy (IFE) requirements for durability, efficiency, and cost. One of the challenging laser components is the pressure foil that...R. Welch, D. V. Rose, and S. Searles, "Electron beam pumped krypton fluoride lasers for fusion energy ," Proc. IEEE, vol. 92, pp. 1043-1056, July...D. Weidenheimer, and D. V. Rose, "Repetitively pulsed, high energy KrF lasers for inertial fusion energy ," Nucl. Fusion, vol. 44, pp. S247-S253

Influence of laser power on microstructure and mechanical properties of laser welded-brazed Mg to Ni coated Ti alloys

NASA Astrophysics Data System (ADS)

Tan, Caiwang; Lu, Qingshuang; Chen, Bo; Song, Xiaoguo; Li, Liqun; Feng, Jicai; Wang, Yang

2017-03-01

AZ31B Magnesium (Mg) and Ti-6Al-4V titanium (Ti) alloys with Ni coating were joined by laser welding-brazing process using AZ92 Mg based filler. The influence of laser power on microstructure and mechanical properties were investigated. Ni coating was found to significantly promote good wetting-spreading ability of molten filler on the Ti sheet. Acceptable joints without obvious defects were obtained within a relatively wide processing window. In the process metallurgical bonding was achieved by the formation of Ti3Al phase at direct irradiation zone and Al-Ni phase followed by a layer of Mg-Al-Ni ternary compound adjacent to the fusion zone at the intermediate zone. The thickness of reaction layers increased slowly with the increasing laser power. The tensile-shear test indicated that joints produced at the laser power of 1300 W reached 2387 N fracture load, representing 88.5% joint efficiency with respect to the Mg base metal. The corresponding failure occurred in the fusion zone of the Mg base metal, while joints fractured at the interface at lower/higher laser power due to the crack or excessive intermetallic compound (IMC) formation along the interface.

Experimental study of fusion neutron and proton yields produced by petawatt-laser-irradiated D₂-³He or CD₄-³He clustering gases.

PubMed

Bang, W; Barbui, M; Bonasera, A; Quevedo, H J; Dyer, G; Bernstein, A C; Hagel, K; Schmidt, K; Gaul, E; Donovan, M E; Consoli, F; De Angelis, R; Andreoli, P; Barbarino, M; Kimura, S; Mazzocco, M; Natowitz, J B; Ditmire, T

2013-09-01

We report on experiments in which the Texas Petawatt laser irradiated a mixture of deuterium or deuterated methane clusters and helium-3 gas, generating three types of nuclear fusion reactions: D(d,^{3}He)n, D(d,t)p, and ^{3}He(d,p)^{4}He. We measured the yields of fusion neutrons and protons from these reactions and found them to agree with yields based on a simple cylindrical plasma model using known cross sections and measured plasma parameters. Within our measurement errors, the fusion products were isotropically distributed. Plasma temperatures, important for the cross sections, were determined by two independent methods: (1) deuterium ion time of flight and (2) utilizing the ratio of neutron yield to proton yield from D(d,^{3}He)n and ^{3}He(d,p)^{4}He reactions, respectively. This experiment produced the highest ion temperature ever achieved with laser-irradiated deuterium clusters.

Development of Laser Based Plasma Diagnostics for Fusion Research on NSTX-U

NASA Astrophysics Data System (ADS)

Barchfeld, Robert Adam

Worldwide demand for power, and in particular electricity, is growing. Increasing population, expanding dependence on electrical devices, as well as the development of emerging nations, has created significant challenges for the power production. Compounding the issue are concerns over pollution, natural resource supplies, and political obstacles in troubled parts of the world. Many believe that investment in renewable energy will solve the expected energy crisis; however, renewable energy has many shortfalls. Consequently, additional sources of energy should be explored to provide the best options for the future. Electricity from fusion power offers many advantages over competing technologies. It can potentially produce large amounts of clean energy, without the serious concerns of fission power plant safety and nuclear waste. Fuel supplies for fusion are plentiful. Fusion power plants can be operated as needed, without dependence on location, or local conditions. However, there are significant challenges before fusion can be realized. Many factors currently limit the effectiveness of fusion power, which prevents a commercial power plant from being feasible. Scientists in many countries have built, and operate, experimental fusion plants to study the fusion process. The leading examples are magnetic confinement reactors known as tokamaks. At present, reactor gain is near unity, where the fusion power output is nearly the same as the power required to operate the reactor. A tenfold increase in gain is what reactors such as ITER hope to achieve, where 50 MW will be used for plasma heating, magnetic fields, and so forth, with a power output of 500 MW. Before this can happen, further research is required. Loss of particle and energy confinement is a principal cause of low performance; therefore, increasing confinement time is key. There are many causes of thermal and particle transport that are being researched, and the prime tools for conducting this research are plasma diagnostics. Plasma diagnostics collect data from fusion reactors in a number of different ways. Among these are far infrared (FIR) laser based systems. By probing a fusion plasma with FIR lasers, many properties can be measured, such as density and density fluctuations. This dissertation discusses the theory and design of two laser based diagnostic instruments: 1) the Far Infrared Tangential Interferometer and Polarimeter (FIReTIP) systems, and 2) the High-ktheta Scattering System. Both of these systems have been designed and fabricated at UC Davis for use on the National Spherical Torus Experiment - Upgrade (NSTX-U), located at Princeton Plasma Physics Laboratory (PPPL). These systems will aid PPPL scientists in fusion research. The FIReTIP system uses 119 ?m methanol lasers to pass through the plasma core to measure a chord averaged plasma density through interferometry. It can also measure the toroidal magnetic field strength by the way of polarimetery. The High-ktheta Scattering System uses a 693 GHz formic acid laser to measure electron scale turbulence. Through collective Thomson scattering, as the probe beam passes through the plasma, collective electron motion will scatter power to a receiver with the angle determined by the turbulence wavenumber. This diagnostic will measure ktheta from 7 to 40 cm-1 with a 4-channel receiver array. The High-ktheta Scattering system was designed to facilitate research on electron temperature gradient (ETG) modes, which are believed to be a major contributor to anomalous transport on NSTX-U. The design and testing of these plasma diagnostics are described in detail. There are a broad range of components detailed including: optically pumped gas FIR lasers, overmoded low loss waveguide, launching and receiving optical designs, quasi-optical mixers, electronics, and monitoring and control systems. Additionally, details are provided for laser maintenance, alignment techniques, and the fundamentals of nano-CNC-machining.

External Heat Transfer Coefficient Measurements on a Surrogate Indirect Inertial Confinement Fusion Target

DOE PAGES

Miles, Robin; Havstad, Mark; LeBlanc, Mary; ...

2015-09-15

External heat transfer coefficients were measured around a surrogate Indirect inertial confinement fusion (ICF) based on the Laser Inertial Fusion Energy (LIFE) design target to validate thermal models of the LIFE target during flight through a fusion chamber. Results indicate that heat transfer coefficients for this target 25-50 W/m 2∙K are consistent with theoretically derived heat transfer coefficients and valid for use in calculation of target heating during flight through a fusion chamber.

A laser device for fusion of nasal mucosa

NASA Astrophysics Data System (ADS)

Sooklal, Valmiki; McClure, Jesse; Hooper, Luke; Larson, Michael

2010-02-01

A prototype device has been created to fuse septal tissue membranes as an alternative to sutures or staples through the controlled application of laser heating and pressure to induce protein denaturation and subsequent tissue fusion, through renaturation and intertwining, across the interface. Lasers have been used to close wounds in controlled laboratory tests over the last 15 years. Many encouraging results have been obtained; however, no commercial delivery systems are currently available. This is due primarily to two factors: requiring an inordinate amount of experience on the part of the operator, and attempting to achieve general applicability for multiple tissue systems. The present device overcomes these barriers as it is tailored for the particular application of septal laser fusion, namely for the coaptation of mucoperichondrial membranes. The important parameters involved in fusing biological tissues are identified. The development of the device followed from computational modeling based on Monte Carlo simulation of photon transport and on engineering firstprinciples. Experiments were designed and analyzed using orthogonal arrays, employing a subset of the relevant parameters, i.e., laser irradiance, dwell time and spot size, for a range of wavelengths. The in vitro fusion experiments employed 1cm by 1cm sections of equine nasal mucosa having a nominal thickness of 1mm.

On the enhancement of p-11B fusion reaction rate in laser-driven plasma by α → p collisional energy transfer

NASA Astrophysics Data System (ADS)

Belloni, Fabio; Margarone, Daniele; Picciotto, Antonino; Schillaci, Francesco; Giuffrida, Lorenzo

2018-02-01

The possibility of triggering an avalanche reaction in laser-driven p-11B fusion by the effect of collisional energy transfer from α particles to protons has recently been debated, especially in connection to the high yield of α particles (4 × 108 per laser shot) achieved on engineered targets at the Prague Asterix Laser System (PALS), with a pulse of 500 J, 0.3 ns FWHM. We elucidate this controversial subject within the framework of a simple two-population model for protons, based on the binary collision theory in a plasma. We find an avalanche characteristic time of almost 1 μs for the 675 keV fusion cross section resonance in typical PALS plasma, upon idealized confinement conditions. This avalanche time is one order of magnitude higher than previously reported, meaning that no such process can substantially develop in plasma at the PALS on the 675 keV resonance, not even in the most optimistic confinement scenarios. Nevertheless, we put forward for further investigation that more realistic conditions for setting up the avalanche regime could rather be attained by suitably targeting the narrow 163 keV resonance in the fusion cross section, also in connection to recently proposed laser-driven magnetic trapping techniques.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Kezhao; Ni, Longchang; Lei, Zhenglong, E-ma

The tensile deformation behavior of laser welded Ti{sub 2}AlNb joints was investigated using in situ analysis methods. The fracture mode of the single-B2-phase fusion zone was quasi-cleavage at room temperature and intergranular at 650 °C, while that of base metal was microvoid coalescence at both room temperature and 650 °C. Tensile deformation at room temperature was observed using in situ SEM tensile testing. In base metal, microcracks nucleated and propagated mainly within the O phase or along O/B2 phase boundaries. While both the cross- and multi-slips were found in the single-B2-phase fusion zone, a confocal laser scanning microscopy was usedmore » to observe the crack initiation and propagation process in situ at 650 °C. Cracks mainly formed along the B2/O phase boundaries in base metal, along the fragile grain boundaries of B2 phase in the fusion zone. The thermal simulation experiment and following TEM analysis indicated that the precipitation of continuous O-phase films along the B2 grain boundaries resulted in the high temperature brittleness of laser welded Ti{sub 2}AlNb joints. - Highlights: •Cracks formed within O phase or along B2/O boundaries in the base metal. •Cross- and multi-slips relieved stress in the fusion zone at room temperature. •Cracks mainly formed along the B2/O boundaries at 650 °C. •In the fusion zone, intergranular cracks were in situ observed at 650 °C. •O-phase films along B2 grain boundaries caused the high temperature brittleness.« less

Green and Fast Laser Fusion Technique for Bulk Silicate Rock Analysis by Laser Ablation-Inductively Coupled Plasma Mass Spectrometry.

PubMed

Zhang, Chenxi; Hu, Zhaochu; Zhang, Wen; Liu, Yongsheng; Zong, Keqing; Li, Ming; Chen, Haihong; Hu, Shenghong

2016-10-18

Sample preparation of whole-rock powders is the major limitation for their accurate and precise elemental analysis by laser ablation inductively-coupled plasma mass spectrometry (ICPMS). In this study, a green, efficient, and simplified fusion technique using a high energy infrared laser was developed for major and trace elemental analysis. Fusion takes only tens of milliseconds for each sample. Compared to the pressed pellet sample preparation, the analytical precision of the developed laser fusion technique is higher by an order of magnitude for most elements in granodiorite GSP-2. Analytical results obtained for five USGS reference materials (ranging from mafic to intermediate to felsic) using the laser fusion technique generally agree with recommended values with discrepancies of less than 10% for most elements. However, high losses (20-70%) of highly volatile elements (Zn and Pb) and the transition metal Cu are observed. The achieved precision is within 5% for major elements and within 15% for most trace elements. Direct laser fusion of rock powders is a green and notably simple method to obtain homogeneous samples, which will significantly accelerate the application of laser ablation ICPMS for whole-rock sample analysis.

The defects and microstructure in the fusion zone of multipass laser welded joints with Inconel 52M filler wire for nuclear power plants

NASA Astrophysics Data System (ADS)

Li, Gang; Lu, Xiaofeng; Zhu, Xiaolei; Huang, Jian; Liu, Luwei; Wu, Yixiong

2017-09-01

The defects and microstructure in the fusion zone of multipass laser welded joints with Inconel 52M filler wire are investigated for nuclear power plants. Experimental results indicate that the incomplete fusion forms as the deposited metals do not completely cover the groove during multipass laser welding. The dendritic morphologies are observed on the inner surface of the porosity in the fusion zone. Many small cellular are found in the zones near the fusion boundary. With solidification preceding, cellular gradually turn into columnar dendrites and symmetrical columnar dendrites are exhibited in the weld center of the fusion zone. The fine equiaxed grains form and columnar dendrites disappear in the remelted zone of two passes. The dendrite arm spacing in the fusion zone becomes widened with increasing welding heat input. Nb-rich carbides/carbonitrides are preferentially precipitated in the fusion zone of multipass laser welded joints. In respect to high cooling rate during multipass laser welding, element segregation could be insufficient to achieve the component of Laves phase.

[Three-dimensional tooth model reconstruction based on fusion of dental computed tomography images and laser-scanned images].

PubMed

Zhang, Dongxia; Gan, Yangzhou; Xiong, Jing; Xia, Zeyang

2017-02-01

Complete three-dimensional(3D) tooth model provides essential information to assist orthodontists for diagnosis and treatment planning. Currently, 3D tooth model is mainly obtained by segmentation and reconstruction from dental computed tomography(CT) images. However, the accuracy of 3D tooth model reconstructed from dental CT images is low and not applicable for invisalign design. And another serious problem also occurs, i.e. frequentative dental CT scan during different intervals of orthodontic treatment often leads to radiation to the patients. Hence, this paper proposed a method to reconstruct tooth model based on fusion of dental CT images and laser-scanned images. A complete3 D tooth model was reconstructed with the registration and fusion between the root reconstructed from dental CT images and the crown reconstructed from laser-scanned images. The crown of the complete 3D tooth model reconstructed with the proposed method has higher accuracy. Moreover, in order to reconstruct complete 3D tooth model of each orthodontic treatment interval, only one pre-treatment CT scan is needed and in the orthodontic treatment process only the laser-scan is required. Therefore, radiation to the patients can be reduced significantly.

Laser Light-field Fusion for Wide-field Lensfree On-chip Phase Contrast Microscopy of Nanoparticles

NASA Astrophysics Data System (ADS)

Kazemzadeh, Farnoud; Wong, Alexander

2016-12-01

Wide-field lensfree on-chip microscopy, which leverages holography principles to capture interferometric light-field encodings without lenses, is an emerging imaging modality with widespread interest given the large field-of-view compared to lens-based techniques. In this study, we introduce the idea of laser light-field fusion for lensfree on-chip phase contrast microscopy for detecting nanoparticles, where interferometric laser light-field encodings acquired using a lensfree, on-chip setup with laser pulsations at different wavelengths are fused to produce marker-free phase contrast images of particles at the nanometer scale. As a proof of concept, we demonstrate, for the first time, a wide-field lensfree on-chip instrument successfully detecting 300 nm particles across a large field-of-view of ~30 mm2 without any specialized or intricate sample preparation, or the use of synthetic aperture- or shift-based techniques.

Laser Light-field Fusion for Wide-field Lensfree On-chip Phase Contrast Microscopy of Nanoparticles.

PubMed

Kazemzadeh, Farnoud; Wong, Alexander

2016-12-13

Wide-field lensfree on-chip microscopy, which leverages holography principles to capture interferometric light-field encodings without lenses, is an emerging imaging modality with widespread interest given the large field-of-view compared to lens-based techniques. In this study, we introduce the idea of laser light-field fusion for lensfree on-chip phase contrast microscopy for detecting nanoparticles, where interferometric laser light-field encodings acquired using a lensfree, on-chip setup with laser pulsations at different wavelengths are fused to produce marker-free phase contrast images of particles at the nanometer scale. As a proof of concept, we demonstrate, for the first time, a wide-field lensfree on-chip instrument successfully detecting 300 nm particles across a large field-of-view of ~30 mm 2 without any specialized or intricate sample preparation, or the use of synthetic aperture- or shift-based techniques.

Optimization of the neutron yield in fusion plasmas produced by Coulomb explosions of deuterium clusters irradiated by a petawatt laser.

PubMed

Bang, W; Dyer, G; Quevedo, H J; Bernstein, A C; Gaul, E; Donovan, M; Ditmire, T

2013-02-01

The kinetic energy of hot (multi-keV) ions from the laser-driven Coulomb explosion of deuterium clusters and the resulting fusion yield in plasmas formed from these exploding clusters has been investigated under a variety of conditions using the Texas Petawatt laser. An optimum laser intensity was found for producing neutrons in these cluster fusion plasmas with corresponding average ion energies of 14 keV. The substantial volume (1-10 mm(3)) of the laser-cluster interaction produced by the petawatt peak power laser pulse led to a fusion yield of 1.6×10(7) neutrons in a single shot with a 120 J, 170 fs laser pulse. Possible effects of prepulses are discussed.

Direct Drive Fusion Energy Shock Ignition Designs for Sub-MJ Lasers

DTIC Science & Technology

2008-09-01

FUSION ENERGY SHOCK IGNITION DESIGNS FOR SUB-MJ LASERS Andrew J. Schmitt, J. W. Bates, S. P. Obenschain, and S. T. Zalesak Plasma Physics Division, Naval Research Laboratory, Washington DC 20375 andrew.schmitt@nrl.navy.mil D. E. Fyfe LCP&FD, Naval Research Laboratory, Washington DC 20375 R. Betti Fusion Science Center and Laboratory for Laser Energetics, University of Rochester, Rochester NY New approaches in target design have increased the pos- sibility that useful fusion power can be generated with sub-MJ lasers. We have performed many 1D and 2D

Temperature characteristics of fusion splicing Hollow Core Photonic Crystal Fiber by sinusoidal modulation CO2 laser

NASA Astrophysics Data System (ADS)

Fu, Guangwei; Li, Kuixing; Fu, Xinghu; Bi, Weihong

2013-07-01

During the fusion splicing Hollow Core Photonic Crystal Fiber (HC-PCF), the air-holes collapse easily due to the improper fusion duration time and optical power. To analyze the temperature characteristics of fusion splicing HC-PCF, a heating method by sinusoidal modulation CO2 laser has been proposed. In the sinusoidal modulation, the variation relationships among laser power, temperature difference and angular frequency are analyzed. The results show that the theoretical simulation is basically in accordance with the experimental data. Therefore, a low-loss fusion splicing can be achieved by modulating the CO2 laser frequency to avoid the air-holes collapse of HC-PCF. Further, the errors are also given.

Surface imaging, laser positioning or volumetric imaging for breast cancer with nodal involvement treated by helical TomoTherapy.

PubMed

Crop, Frederik; Pasquier, David; Baczkiewic, Amandine; Doré, Julie; Bequet, Lena; Steux, Emeline; Gadroy, Anne; Bouillon, Jacqueline; Florence, Clement; Muszynski, Laurence; Lacour, Mathilde; Lartigau, Eric

2016-09-08

A surface imaging system, Catalyst (C-Rad), was compared with laser-based positioning and daily mega voltage computed tomography (MVCT) setup for breast patients with nodal involvement treated by helical TomoTherapy. Catalyst-based positioning performed better than laser-based positioning. The respective modalities resulted in a standard deviation (SD), 68% confidence interval (CI) of positioning of left-right, craniocaudal, anterior-posterior, roll: 2.4 mm, 2.7 mm, 2.4 mm, 0.9° for Catalyst positioning, and 6.1 mm, 3.8 mm, 4.9 mm, 1.1° for laser-based positioning, respectively. MVCT-based precision is a combination of the interoperator variability for MVCT fusion and the patient movement during the time it takes for MVCT and fusion. The MVCT fusion interoperator variability for breast patients was evaluated at one SD left-right, craniocaudal, ant-post, roll as: 1.4 mm, 1.8 mm, 1.3 mm, 1.0°. There was no statistically significant difference between the automatic MVCT registration result and the manual adjustment; the automatic fusion results were within the 95% CI of the mean result of 10 users, except for one specific case where the patient was positioned with large yaw. We found that users add variability to the roll correction as the automatic registration was more consistent. The patient position uncertainty confidence interval was evaluated as 1.9 mm, 2.2 mm, 1.6 mm, 0.9° after 4 min, and 2.3 mm, 2.8 mm, 2.2 mm, 1° after 10 min. The combination of this patient movement with MVCT fusion interoperator variability results in total standard deviations of patient posi-tion when treatment starts 4 or 10 min after initial positioning of, respectively: 2.3 mm, 2.8 mm, 2.0 mm, 1.3° and 2.7 mm, 3.3 mm, 2.6 mm, 1.4°. Surface based positioning arrives at the same precision when taking into account the time required for MVCT imaging and fusion. These results can be used on a patient-per-patient basis to decide which positioning system performs the best after the first 5 fractions and when daily MVCT can be omitted. Ideally, real-time monitoring is required to reduce important intrafraction movement. © 2016 The Authors.

On the feasibility of a fiber-based inertial fusion laser driver

NASA Astrophysics Data System (ADS)

Labaune, C.; Hulin, D.; Galvanauskas, A.; Mourou, G. A.

2008-08-01

One critical issue for the realization of Inertial Fusion Energy (IFE) power plants is the driver efficiency. High driver efficiency will greatly relax the driver energy requested to produce a fusion gain, resulting in more compact and less costly facilities. Among lasers, systems based on guided wave such as diode pumped Yb:glass fiber-amplifiers with a demonstrated overall efficiency close to 70% as opposed to few percents for systems based on free propagation, offer some intriguing opportunities. Guided optics provides the enormous advantage to directly benefit from the telecommunication industry where components are made cheap, rugged, well tested, environmentally stable, with lifetimes measured in tens of years and compatible with massive manufacturing. In this paper, we are studying the possibility to design a laser driver solely based on guided wave optics. We call this concept FAN for Fiber Amplification Network. It represents a profound departure from already proposed laser drivers all based on free propagation optics. The system will use a large number of identical fibers to combines long (ns) and short (ps) pulses that are needed for the fast ignition scheme. Technical details are discussed relative to fiber type, pump, phasing, pulse shaping and timing as well as fiber distribution around the chamber. The proposed fiber driver provides maximum and independent control on the wavefront, pulse duration, pulse shape, timing, making possible reaching the highest gain. The massive manufacturing will be amenable to a cheaper facility with an easy upkeep.

Numerical and experimental analysis of fusion offset in splicing photonic crystal fiber with CO2 laser

NASA Astrophysics Data System (ADS)

Jin, Wa; Bi, Weihong; Fu, Guangwei

2014-09-01

Single mode fibers (SMFs) need more fusion energy than PCFs during a splicing process, and it is necessary to make some offsets of the center of heat source toward to the SMFs. Based on the study of characteristics of heat transfer of PCFs and SMFs during splicing process with CO2 laser as the heat source, this paper reports the first systematic analysis of the optimal splicing offset of splicing SMFs and PCFs in theory and experiments. The results show that fusion splicing offsets can be applied to control the air-hole collapse and realize the practical splicing process between PCFs and SMFs with low loss.

An overview of LLNL high-energy short-pulse technology for advanced radiography of laser fusion experiments

NASA Astrophysics Data System (ADS)

Barty, C. P. J.; Key, M.; Britten, J.; Beach, R.; Beer, G.; Brown, C.; Bryan, S.; Caird, J.; Carlson, T.; Crane, J.; Dawson, J.; Erlandson, A. C.; Fittinghoff, D.; Hermann, M.; Hoaglan, C.; Iyer, A.; Jones, L., II; Jovanovic, I.; Komashko, A.; Landen, O.; Liao, Z.; Molander, W.; Mitchell, S.; Moses, E.; Nielsen, N.; Nguyen, H.-H.; Nissen, J.; Payne, S.; Pennington, D.; Risinger, L.; Rushford, M.; Skulina, K.; Spaeth, M.; Stuart, B.; Tietbohl, G.; Wattellier, B.

2004-12-01

The technical challenges and motivations for high-energy, short-pulse generation with NIF and possibly other large-scale Nd : glass lasers are reviewed. High-energy short-pulse generation (multi-kilojoule, picosecond pulses) will be possible via the adaptation of chirped pulse amplification laser techniques on NIF. Development of metre-scale, high-efficiency, high-damage-threshold final optics is a key technical challenge. In addition, deployment of high energy petawatt (HEPW) pulses on NIF is constrained by existing laser infrastructure and requires new, compact compressor designs and short-pulse, fibre-based, seed-laser systems. The key motivations for HEPW pulses on NIF is briefly outlined and includes high-energy, x-ray radiography, proton beam radiography, proton isochoric heating and tests of the fast ignitor concept for inertial confinement fusion.

Fusion reactions initiated by laser-accelerated particle beams in a laser-produced plasma.

PubMed

Labaune, C; Baccou, C; Depierreux, S; Goyon, C; Loisel, G; Yahia, V; Rafelski, J

2013-01-01

The advent of high-intensity-pulsed laser technology enables the generation of extreme states of matter under conditions that are far from thermal equilibrium. This in turn could enable different approaches to generating energy from nuclear fusion. Relaxing the equilibrium requirement could widen the range of isotopes used in fusion fuels permitting cleaner and less hazardous reactions that do not produce high-energy neutrons. Here we propose and implement a means to drive fusion reactions between protons and boron-11 nuclei by colliding a laser-accelerated proton beam with a laser-generated boron plasma. We report proton-boron reaction rates that are orders of magnitude higher than those reported previously. Beyond fusion, our approach demonstrates a new means for exploring low-energy nuclear reactions such as those that occur in astrophysical plasmas and related environments.

Femtosecond laser-induced fusion of nonadherent cells and two-cell porcine embryos.

PubMed

Kuetemeyer, Kai; Lucas-Hahn, Andrea; Petersen, Bjoern; Niemann, Heiner; Heisterkamp, Alexander

2011-08-01

Cell fusion is a fundamental biological process that can be artificially induced by different methods. Although femtosecond (fs) lasers have been successfully employed for cell fusion over the past few years, the underlying mechanisms are still unknown. In our experimental study, we investigated the correlation between fs laser-induced cell fusion and membrane perforation, and the influence of laser parameters on the fusion efficiency of nonadherent HL-60 cells. We found that shorter exposure times resulted in higher fusion efficiencies with a maximum of 21% at 10 ms and 100 mJ/cm(2) (190 mW). Successful cell fusion was indicated by the formation of a long-lasting vapor bubble in the irradiated area with an average diameter much larger than in cell perforation experiments. With this knowledge, we demonstrated, for the first time, the fusion of very large parthenogenetic two-cell porcine embryos with high efficiencies of 55% at 20 ms and 360 mJ/cm(2) (670 mW). Long-term viability of fused embryos was proven by successful development up to the blastocyst stage in 70% of cases with no significant difference to controls. In contrast to previous studies, our results indicate that fs laser-induced cell fusion occurs when the membrane pore size exceeds a critical value, preventing immediate membrane resealing.

1 Hz fast-heating fusion driver HAMA pumped by a 10 J green diode-pumped solid-state laser

NASA Astrophysics Data System (ADS)

Mori, Y.; Sekine, T.; Komeda, O.; Nakayama, S.; Ishii, K.; Hanayama, R.; Fujita, K.; Okihara, S.; Satoh, N.; Kurita, T.; Kawashima, T.; Kan, H.; Nakamura, N.; Kondo, T.; Fujine, M.; Azuma, H.; Hioki, T.; Kakeno, M.; Motohiro, T.; Nishimura, Y.; Sunahara, A.; Sentoku, Y.; Kitagawa, Y.

2013-07-01

A Ti : sapphire laser HAMA pumped by a diode-pumped solid-state laser (DPSSL) is developed to enable a high-repetitive inertial confinement fusion (ICF) experiment to be conducted. To demonstrate a counter-irradiation fast-heating fusion scheme, a 3.8 J, 0.4 ns amplified chirped pulse is divided into four beams: two counter-irradiate a target with intensities of 6 × 1013 W cm-2, and the remaining two are pulse-compressed to 110 fs for heating the imploded target with intensities of 2 × 1017 W cm-2. HAMA contributed to the first demonstration by showing that a 10 J class DPSSL is adaptable to ICF experiments and succeeded in DD neutron generation in the repetition mode. Based on HAMA, we can design and develop an integrated repetitive ICF experiment machine by including target injection and tracking.

Neutronics Design of a Thorium-Fueled Fission Blanket for LIFE (Laser Inertial Fusion-based Energy)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Powers, J; Abbott, R; Fratoni, M

The Laser Inertial Fusion-based Energy (LIFE) project at LLNL includes development of hybrid fusion-fission systems for energy generation. These hybrid LIFE engines use high-energy neutrons from laser-based inertial confinement fusion to drive a subcritical blanket of fission fuel that surrounds the fusion chamber. The fission blanket contains TRISO fuel particles packed into pebbles in a flowing bed geometry cooled by a molten salt (flibe). LIFE engines using a thorium fuel cycle provide potential improvements in overall fuel cycle performance and resource utilization compared to using depleted uranium (DU) and may minimize waste repository and proliferation concerns. A preliminary engine designmore » with an initial loading of 40 metric tons of thorium can maintain a power level of 2000 MW{sub th} for about 55 years, at which point the fuel reaches an average burnup level of about 75% FIMA. Acceptable performance was achieved without using any zero-flux environment 'cooling periods' to allow {sup 233}Pa to decay to {sup 233}U; thorium undergoes constant irradiation in this LIFE engine design to minimize proliferation risks and fuel inventory. Vast reductions in end-of-life (EOL) transuranic (TRU) inventories compared to those produced by a similar uranium system suggest reduced proliferation risks. Decay heat generation in discharge fuel appears lower for a thorium LIFE engine than a DU engine but differences in radioactive ingestion hazard are less conclusive. Future efforts on development of thorium-fueled LIFE fission blankets engine development will include design optimization, fuel performance analysis work, and further waste disposal and nonproliferation analyses.« less

Scaling of Fiber Laser Systems Based on Novel Components and High Power Capable Packaging and Joining Technologies

DTIC Science & Technology

2010-09-01

l ri Laser Splicing / Welding r li i / l i Contact Bonding t t i Wafer Level Bonding Mineralic, Fusion . Anodic, Eutectic, Glass-frit, liquid...28-29 September 2010 SET-171 Mid-IR Fiber Laser Workshop partly sponsored by Tapering and splicing device as well as process control developed...Components Laser based splicing and tapering Multimode fiber (ø720µm) with spliced end cap (ø1500µm) © Fraunhofer IOF 28-29 September 2010 SET-171 Mid-IR

Scientific and technological advancements in inertial fusion energy

DOE PAGES

Hinkel, D. E.

2013-09-26

Scientific advancements in inertial fusion energy (IFE) were reported on at the IAEA Fusion Energy Conference, October 2012. Results presented transect the different ways to assemble the fuel, different scenarios for igniting the fuel, and progress in IFE technologies. The achievements of the National Ignition Campaign within the USA, using the National Ignition Facility (NIF) to indirectly drive laser fusion, have found beneficial the achievements in other IFE arenas such as directly driven laser fusion and target fabrication. Moreover, the successes at NIF have pay-off to alternative scenarios such as fast ignition, shock ignition, and heavy-ion fusion as well asmore » to directly driven laser fusion. As a result, this synergy is summarized here, and future scientific studies are detailed.« less

III International Conference on Laser and Plasma Researches and Technologies

NASA Astrophysics Data System (ADS)

2017-12-01

A.P. Kuznetsov and S.V. Genisaretskaya III Conference on Plasma and Laser Research and Technologies took place on January 24th until January 27th, 2017 at the National Research Nuclear University "MEPhI" (NRNU MEPhI). The Conference was organized by the Institute for Laser and Plasma Technologies and was supported by the Competitiveness Program of NRNU MEPhI. The conference program consisted of nine sections: • Laser physics and its application • Plasma physics and its application • Laser, plasma and radiation technologies in industry • Physics of extreme light fields • Controlled thermonuclear fusion • Modern problems of theoretical physics • Challenges in physics of solid state, functional materials and nanosystems • Particle accelerators and radiation technologies • Modern trends of quantum metrology. The conference is based on scientific fields as follows: • Laser, plasma and radiation technologies in industry, energetic, medicine; • Photonics, quantum metrology, optical information processing; • New functional materials, metamaterials, “smart” alloys and quantum systems; • Ultrahigh optical fields, high-power lasers, Mega Science facilities; • High-temperature plasma physics, environmentally-friendly energetic based on controlled thermonuclear fusion; • Spectroscopic synchrotron, neutron, laser research methods, quantum mechanical calculation and computer modelling of condensed media and nanostructures. More than 250 specialists took part in the Conference. They represented leading Russian scientific research centers and universities (National Research Centre "Kurchatov Institute", A.M. Prokhorov General Physics Institute, P.N. Lebedev Physical Institute, Troitsk Institute for Innovation and Fusion Research, Joint Institute for Nuclear Research, Moscow Institute of Physics and Tecnology and others) and leading scientific centers and universities from Germany, France, USA, Canada, Japan. We would like to thank heartily all of the speakers, participants, organizing and program committee members for their contribution to the conference.

Electra: Repetitively Pulsed 700 J, 100 ns Electron Beam Pumped KrF Laser

DTIC Science & Technology

2006-05-01

the Inertial Fusion Energy (IFE) requirements for durability, efficiency, and cost. The technologies developed on Electra should be directly scalable...and S. Searles, "Electron beam pumped krypton fluoride lasers for fusion energy ," Proc. IEEE, vol. 92, pp. 1043-1056, July 2004. [2] M.C. Myers, J.D...34Repetitively pulsed, high energy KrF lasers for inertial fusion energy ," Nucl. Fusion, vol. 44, pp. S247-S253, November 2004. [3] J.D. Sethian, M

Determination of elemental content off rocks by laser ablation inductively coupled plasma mass spectrometry

USGS Publications Warehouse

Lichte, F.E.

1995-01-01

A new method of analysis for rocks and soils is presented using laser ablation inductively coupled plasma mass spectrometry. It is based on a lithium borate fusion and the free-running mode of a Nd/YAG laser. An Ar/N2 sample gas improves sensitivity 7 ?? for most elements. Sixty-three elements are characterized for the fusion, and 49 elements can be quantified. Internal standards and isotopic spikes ensure accurate results. Limits of detection are 0.01 ??g/g for many trace elements. Accuracy approaches 5% for all elements. A new quality assurance procedure is presented that uses fundamental parameters to test relative response factors for the calibration.

Characteristics of Laser Beam and Friction Stir Welded AISI 409M Ferritic Stainless Steel Joints

NASA Astrophysics Data System (ADS)

Lakshminarayanan, A. K.; Balasubramanian, V.

2012-04-01

This article presents the comparative evaluation of microstructural features and mechanical properties of friction stir welded (solid-state) and laser beam welded (high energy density fusion welding) AISI 409M grade ferritic stainless steel joints. Optical microscopy, microhardness testing, transverse tensile, and impact tests were performed. The coarse ferrite grains in the base material were changed to fine grains consisting duplex structure of ferrite and martensite due to the rapid cooling rate and high strain induced by severe plastic deformation caused by frictional stirring. On the other hand, columnar dendritic grain structure was observed in fusion zone of laser beam welded joints. Tensile testing indicates overmatching of the weld metal relative to the base metal irrespective of the welding processes used. The LBW joint exhibited superior impact toughness compared to the FSW joint.

Recent advances in the front-end sources of the LMJ fusion laser

NASA Astrophysics Data System (ADS)

Gleyze, Jean-François; Hares, Jonathan; Vidal, Sebastien; Beck, Nicolas; Dubertrand, Jerome; Perrin, Arnaud

2011-03-01

LMJ is typical of lasers used for inertial confinement fusion and requires a laser of programmable parameters for injection into the main amplifier. For several years, the CEA has developed front end fiber sources, based on telecommunications fiber optics technologies. These sources meet the needs but as the technology evolves we can expect improved efficiency and reductions in size and cost. We give an up-to-date description of some present development issues, particularly in the field of temporal shaping with the use of digital system. The synchronization of such electronics has been challenging however we now obtain system jitter of less then 7ps rms. Secondly, we will present recent advance in the use of fiber based pre-comp system to avoid parasitic amplitude modulation from phase modulation used for spectral broadening.

LLE 1998 annual report, October 1997--September 1998. Inertial fusion program and National Laser Users` Facility program

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1999-01-01

This report summarizes research at the Laboratory for Laser Energetics (LLE), the operation of the National Laser Users` Facility (NLUF), and programs involving the education of high school, undergraduate, and graduate students for FY98. Research summaries cover: progress in laser fusion; diagnostic development; laser and optical technology; and advanced technology for laser targets.

Chromophore-assisted laser inactivation of alpha- and gamma-tubulin SNAP-tag fusion proteins inside living cells.

PubMed

Keppler, Antje; Ellenberg, Jan

2009-02-20

Chromophore-assisted laser inactivation (CALI) can help to unravel localized activities of target proteins at defined times and locations within living cells. Covalent SNAP-tag labeling of fusion proteins with fluorophores such as fluorescein is a fast and highly specific tool to attach the photosensitizer to its target protein in vivo for selective inactivation of the fusion protein. Here, we demonstrate the effectiveness and specificity of SNAP-tag-based CALI by acute inactivation of alpha-tubulin and gamma-tubulin SNAP-tag fusions during live imaging assays of cell division. Singlet oxygen is confirmed as the reactive oxygen species that leads to loss of fusion protein function. The major advantage of SNAP-tag CALI is the ease, reliability, and high flexibility in labeling: the genetically encoded protein tag can be covalently labeled with various dyes matching the experimental requirements. This makes SNAP-tag CALI a very useful tool for rapid inactivation of tagged proteins in living cells.

Target Fabrication Technology and New Functional Materials for Laser Fusion and Laser-Plasma Experiment

NASA Astrophysics Data System (ADS)

Nagai, Keiji; Norimatsu, Takayoshi; Izawa, Yasukazu

Target fabrication technique is a key issue of laser fusion. We present a comprehensive, up-to-data compilation of laser fusion target fabrication and relating new materials. To achieve highly efficient laser implosion, organic and inorganic highly spherical millimeter-sized capsules and cryogenic hydrogen layers inside should be uniform in diameter and thickness within sub-micrometer ˜ nanometer error. Porous structured targets and molecular cluster targets are required for laser-plasma experiments and applications. Various technologies and new materials concerning above purposes are summarized including fast-ignition targets, equation-of-state measurement targets, high energy ion generation targets, etc.

Development scenario for laser fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maniscalco, J.A.; Hovingh, J.; Buntzen, R.R.

1976-03-30

This scenario proposes establishment of test and engineering facilities to (1) investigate the technological problems associated with laser fusion, (2) demonstrate fissile fuel production, and (3) demonstrate competitive electrical power production. Such facilities would be major milestones along the road to a laser-fusion power economy. The relevant engineering and economic aspects of each of these research and development facilities are discussed. Pellet design and gain predictions corresponding to the most promising laser systems are presented for each plant. The results show that laser fusion has the potential to make a significant contribution to our energy needs. Beginning in the earlymore » 1990's, this new technology could be used to produce fissile fuel, and after the turn of the century it could be used to generate electrical power.« less

[Element distribution analysis of welded fusion zone by laser-induced breakdown spectroscopy].

PubMed

Yang, Chun; Zhang, Yong; Jia, Yun-Hai; Wang, Hai-Zhou

2014-04-01

Over the past decade there has been intense activity in the study and development of laser-induced breakdown spectroscopy (LIBS). As a new tool for surface microanalysis, it caused widespread in materials science because of the advantage of rapid and high sensitivity. In the present paper, the distribution of Ni, Mn, C and Si near weld fusion line was analyzed on two kinds of weld sample. Line scanning mode analysis was carried out by three different kinds of methods, namely laser-induced breakdown spectroscopy (LIBS), scanning electron microscope/energy dispersive spectrometer (SEM/EDS) and electron probe X-ray microanalyser (EPMA). The concentration variation trend of Ni and Mn acquired by LIBS is coincident with SEM/EDS and EPMA. The result shows that the content of Ni and Mn was significantly different between weld seam and base metal on both the samples. The content of Ni and Mn was much higher in weld seam than in base metal, and a sharp concentration gradient was analyzed in the fusion zone. According to the distribution of Ni and Mn, all the three methods got a similar value of welded fusion zone width. The concentration variation trend of C and Si acquired by LIBS is not coincident with SEM/EDS and EPMA. The concentration difference between weld seam and base metal was analyzed by LIBS, but had not by SEM/EDS and EPMA, because of the low concentration and slight difference. The concentration gradient of C and Si in fusion zone was shows clearly by LIBS. For higher sensitivity performance, LIBS is much more adapted to analyze low content element than SEM/EDS and EPMA.

Method for mounting laser fusion targets for irradiation

DOEpatents

Fries, R. Jay; Farnum, Eugene H.; McCall, Gene H.

1977-07-26

Methods for preparing laser fusion targets of the ball-and-disk type are disclosed. Such targets are suitable for irradiation with one or two laser beams to produce the requisite uniform compression of the fuel material.

Laser program annual report, 1977. Volume 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bender, C.F.; Jarman, B.D.

1978-07-01

An overview is given of the laser fusion program. The solid-state program covers the Shiva and Nova projects. Laser components, control systems, alignment systems, laser beam diagnostics, power conditioning, and optical components are described. The fusion experimental program concerns the diagnostics and data acquisition associated with Argus and Shiva. (MOW)

An Overview of Ni Base Additive Fabrication Technologies for Aerospace Applications (Preprint)

DTIC Science & Technology

2011-03-01

fusion welding processes that have the ability to add filler material can be used as additive manufacturing processes . The majority of the work in the...Laser Additive Manufacturing (LAM) The LAM process uses a conventional laser welding heat source (CO2 or solid state laser) combined with a...wrought properties. The LAM process typically has a lower deposition rate (0.5 – 10 lbs/hr) compared to EB, PTA or TIG based processes , although as

Nonlinear Laser-Plasma Interaction in Magnetized Liner Inertial Fusion

DOE PAGES

Geissel, Matthias; Awe, Thomas James; Bliss, David E.; ...

2016-03-04

Sandia National Laboratories is pursuing a variation of Magneto-Inertial Fusion called Magnetized Liner Inertial Fusion, or MagLIF. The MagLIF approach requires magnetization of the deuterium fuel, which is accomplished by an initial external B-Field and laser-driven pre-heat. Although magnetization is crucial to the concept, it is challenging to couple sufficient energy to the fuel, since laser-plasma instabilities exist, and a compromise between laser spot size, laser entrance window thickness, and fuel density must be found. Ultimately, nonlinear processes in laser plasma interaction, or laser-plasma instabilities (LPI), complicate the deposition of laser energy by enhanced absorption, backscatter, filamentation and beam-spray. Wemore » determine and discuss key LPI processes and mitigation methods. Results with and without improvement measures are presented.« less

Nonlinear Laser-Plasma Interaction in Magnetized Liner Inertial Fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Geissel, Matthias; Awe, Thomas James; Bliss, David E.

Sandia National Laboratories is pursuing a variation of Magneto-Inertial Fusion called Magnetized Liner Inertial Fusion, or MagLIF. The MagLIF approach requires magnetization of the deuterium fuel, which is accomplished by an initial external B-Field and laser-driven pre-heat. Although magnetization is crucial to the concept, it is challenging to couple sufficient energy to the fuel, since laser-plasma instabilities exist, and a compromise between laser spot size, laser entrance window thickness, and fuel density must be found. Ultimately, nonlinear processes in laser plasma interaction, or laser-plasma instabilities (LPI), complicate the deposition of laser energy by enhanced absorption, backscatter, filamentation and beam-spray. Wemore » determine and discuss key LPI processes and mitigation methods. Results with and without improvement measures are presented.« less

Optimal fusion offset in splicing photonic crystal fibers

NASA Astrophysics Data System (ADS)

Jin, Wa; Bi, Weihong; Fu, Guangwei

2013-08-01

Heat transfer is very complicate in fusion splicing process of photonic crystal fibers (PCFs) due to different structures and sizes of air hole, which requires different fusion splicing power and offsets of heat source. Based on the heat transfer characteristics, this paper focus on the optimal splicing offset splicing the single mode fiber and PCFs with a CO2 laser irradiation. The theory and experiments both show that the research results can effectively calculate the optimal fusion splicing offset and guide the practical splicing between PCFs and SMFs.

The HALNA project: Diode-pumped solid-state laser for inertial fusion energy

NASA Astrophysics Data System (ADS)

Kawashima, T.; Ikegawa, T.; Kawanaka, J.; Miyanaga, N.; Nakatsuka, M.; Izawa, Y.; Matsumoto, O.; Yasuhara, R.; Kurita, T.; Sekine, T.; Miyamoto, M.; Kan, H.; Furukawa, H.; Motokoshi, S.; Kanabe, T.

2006-06-01

High-enery, rep.-rated, diode-pumped solid-state laser (DPSSL) is one of leading candidates for inertial fusion energy driver (IFE) and related laser-driven high-field applications. The project for the development of IFE laser driver in Japan, HALNA (High Average-power Laser for Nuclear Fusion Application) at ILE, Osaka University, aims to demonstrate 100-J pulse energy at 10 Hz rep. rate with 5 times diffraction limited beam quality. In this article, the advanced solid-state laser technologies for one half scale of HALNA (50 J, 10 Hz) are presented including thermally managed slab amplifier of Nd:phosphate glass and zig-zag optical geometry, and uniform, large-area diode-pumping.

Frontiers in propulsion research: Laser, matter-antimatter, excited helium, energy exchange thermonuclear fusion

NASA Technical Reports Server (NTRS)

Papailiou, D. D. (Editor)

1975-01-01

Concepts are described that presently appear to have the potential for propulsion applications in the post-1990 era of space technology. The studies are still in progress, and only the current status of investigation is presented. The topics for possible propulsion application are lasers, nuclear fusion, matter-antimatter annihilation, electronically excited helium, energy exchange through the interaction of various fields, laser propagation, and thermonuclear fusion technology.

Reducing parametric backscattering by polarization rotation

DOE PAGES

Barth, Ido; Fisch, Nathaniel J.

2016-10-01

When a laser passes through underdense plasmas, Raman and Brillouin Backscattering can reflect a substantial portion of the incident laser energy. This is a major loss mechanism, for example, in employing lasers in inertial confinement fusion. But, by slow rotation of the incident linear polarization, the overall reflectivity can be reduced significantly. Particle in cell simulations show that, for parameters similar to those of indirect drive fusion experiments, polarization rotation reduces the reflectivity by a factor of 5. A general, fluid-model based analytical estimation for the reflectivity reduction agrees with simulations. However, in identifying the source of the backscatter reduction,more » it is difficult to disentangle the rotating polarization from the frequency separation based approach used to engineer the beam's polarization. Though the backscatter reduction arises similarly to other approaches that employ frequency separation, in the case here, the intensity remains constant in time.« less

Yb:YAG ceramic-based laser driver for Inertial Fusion Energy (IFE)

NASA Astrophysics Data System (ADS)

Vetrovec, John; Copeland, Drew A.; Litt, Amardeep S.

2016-03-01

We report on a new class of laser amplifiers for inertial confinement fusion (ICF) drivers based on a Yb:YAG ceramic disk in an edge-pumped configuration and cooled by a high-velocity gas flow. The Yb lasant offers very high efficiency and low waste heat. The ceramic host material has a thermal conductivity nearly 15-times higher than the traditionally used glass and it is producible in sizes suitable for a typical 10- to 20-kJ driver beam line. The combination of high lasant efficiency, low waste heat, edge-pumping, and excellent thermal conductivity of the host, enable operation at 10 to 20 Hz at over 20% wall plug efficiency while being comparably smaller and less costly than recently considered face-pumped alternative drivers using Nd:glass, Yb:S-FAP, and cryogenic Yb:YAG. Scalability of the laser driver over a broad range of sizes is presented.

Precision operation of the Nova laser for fusion experiments

NASA Astrophysics Data System (ADS)

Caird, J. A.; Ehrlich, R. B.; Hermes, G. L.; Landen, O. L.; Laumann, C. W.; Lerche, R. A.; Miller, J. L.; Murray, J. E.; Nielsen, N. D.; Powell, H. T.; Rushford, M. C.; Saunders, R. L.; Thompson, C. E.; VanArsdall, P. J.; Vann, C. S.; Weiland, T. L.

1994-10-01

The operation of a Neodymium glass laser of a special design for fusion experiments is improved by a better pulse synchronization, the gain stabilization, and the laser diagnostics. We used sensor upgrading and antifriction coating of focusing lenses. The pointing accuracy of the Nova laser meets now our goal for precision operation. (AIP)

Ar-Xe Laser: The Path to a Robust, All-Electric Shipboard Directed Energy Weapon

DTIC Science & Technology

2008-12-18

Krypton Fluoride (KrF) laser for fusion energy and is sponsored by the Department of Energy’s (DOE) High Average Power Laser (HAPL) program. DOE...Electronics Conference, Arlington VA, October 2007. 9. “Electron Beam Pumped Lasers for Fusion Energy and Directed Energy Applications”, presented by

Investigation of the Microstructure of Laser-Arc Hybrid Welded Boron Steel

NASA Astrophysics Data System (ADS)

Son, Seungwoo; Lee, Young Ho; Choi, Dong-Won; Cho, Kuk-Rae; Shin, Seung Man; Lee, Youngseog; Kang, Seong-Hoon; Lee, Zonghoon

2018-05-01

The microstructure of boron steel for automotive driving shaft manufacturing after laser-arc hybrid welding was investigated. Laser-arc hybrid welding technology was applied to 3-mm-thick plates of boron steel, ST35MnB. The temperature distribution of the welding pool was analyzed using the finite element method, and the microstructure of the welded boron steel was characterized using optical microscopy and scanning and transmission electron microscopies. The microstructure of the weld joint was classified into the fusion zone, the heat-affected zone (HAZ), and the base material. At the fusion zone, the bainite grains exist in the martensite matrix and show directionality because of heat input from the welding. The HAZ is composed of smaller grains, and the hardness of the HAZ is greater than that of the fusion zone. We discuss that the measured grain size and the hardness of the HAZ originate from undissolved precipitates that retard the grain growth of austenite.

Development of laser-based techniques for in situ characterization of the first wall in ITER and future fusion devices

NASA Astrophysics Data System (ADS)

Philipps, V.; Malaquias, A.; Hakola, A.; Karhunen, J.; Maddaluno, G.; Almaviva, S.; Caneve, L.; Colao, F.; Fortuna, E.; Gasior, P.; Kubkowska, M.; Czarnecka, A.; Laan, M.; Lissovski, A.; Paris, P.; van der Meiden, H. J.; Petersson, P.; Rubel, M.; Huber, A.; Zlobinski, M.; Schweer, B.; Gierse, N.; Xiao, Q.; Sergienko, G.

2013-09-01

Analysis and understanding of wall erosion, material transport and fuel retention are among the most important tasks for ITER and future devices, since these questions determine largely the lifetime and availability of the fusion reactor. These data are also of extreme value to improve the understanding and validate the models of the in vessel build-up of the T inventory in ITER and future D-T devices. So far, research in these areas is largely supported by post-mortem analysis of wall tiles. However, access to samples will be very much restricted in the next-generation devices (such as ITER, JT-60SA, W7-X, etc) with actively cooled plasma-facing components (PFC) and increasing duty cycle. This has motivated the development of methods to measure the deposition of material and retention of plasma fuel on the walls of fusion devices in situ, without removal of PFC samples. For this purpose, laser-based methods are the most promising candidates. Their feasibility has been assessed in a cooperative undertaking in various European associations under EFDA coordination. Different laser techniques have been explored both under laboratory and tokamak conditions with the emphasis to develop a conceptual design for a laser-based wall diagnostic which is integrated into an ITER port plug, aiming to characterize in situ relevant parts of the inner wall, the upper region of the inner divertor, part of the dome and the upper X-point region.

Green frequency-doubled laser-beam propagation in high-temperature hohlraum plasmas.

PubMed

Niemann, C; Berger, R L; Divol, L; Froula, D H; Jones, O; Kirkwood, R K; Meezan, N; Moody, J D; Ross, J; Sorce, C; Suter, L J; Glenzer, S H

2008-02-01

We demonstrate propagation and small backscatter losses of a frequency-doubled (2omega) laser beam interacting with inertial confinement fusion hohlraum plasmas. The electron temperature of 3.3 keV, approximately a factor of 2 higher than achieved in previous experiments with open geometry targets, approaches plasma conditions of high-fusion yield hohlraums. In this new temperature regime, we measure 2omega laser-beam transmission approaching 80% with simultaneous backscattering losses of less than 10%. These findings suggest that good laser coupling into fusion hohlraums using 2omega light is possible.

Conceptual design and issues of the laser inertial fusion test (LIFT) reactor—targets and chamber systems

NASA Astrophysics Data System (ADS)

Norimatsu, T.; Kozaki, Y.; Shiraga, H.; Fujita, H.; Okano, K.; Members of LIFT Design Team

2017-11-01

We present the conceptual design of an experimental laser fusion plant known as the laser inertial fusion test (LIFT) reactor. The conceptual design aims at technically connecting a single-shot experiment and a commercial power plant. The LIFT reactor is designed on a three-phase scheme, where each phase has specific goals and the dedicated chambers of each phase are driven by the same laser. Technical issues related to the chamber technology including radiation safety to repeat burst mode operation are discussed in this paper.

Generation of Mie size microdroplet aerosols with applications in laser-driven fusion experiments.

PubMed

Higginbotham, A P; Semonin, O; Bruce, S; Chan, C; Maindi, M; Donnelly, T D; Maurer, M; Bang, W; Churina, I; Osterholz, J; Kim, I; Bernstein, A C; Ditmire, T

2009-06-01

We have developed a tunable source of Mie scale microdroplet aerosols that can be used for the generation of energetic ions. To demonstrate this potential, a terawatt Ti:Al2O3 laser focused to 2 x 10(19) W/cm2 was used to irradiate heavy water (D2O) aerosols composed of micron-scale droplets. Energetic deuterium ions, which were generated in the laser-droplet interaction, produced deuterium-deuterium fusion with approximately 2 x 10(3) fusion neutrons measured per joule of incident laser energy.

Microstructure characteristics and mechanical properties of laser-TIG hybrid welded dissimilar joints of Ti-22Al-27Nb and TA15

NASA Astrophysics Data System (ADS)

Zhang, Kezhao; Lei, Zhenglong; Chen, Yanbin; Liu, Ming; Liu, Yang

2015-10-01

Laser-TIG-hybrid-welding (TIG - tungsten inert gas) process was successfully applied to investigate the microstructure and tensile properties of Ti-22Al-27Nb/TA15 dissimilar joints. The HAZ of the arc zone in Ti-22Al-27Nb was characterized by three different regions: single B2, B2+α2 and B2+α2+O, while the single B2 phase region was absent in the HAZ of the laser zone. As for the HAZ in TA15 alloy, the microstructure mainly contained acicular α‧ martensites near the fusion line and partially remained the lamellar structure near the base metal. The fusion zone consisted of B2 phase due to the relatively high content of β phase stabilizing elements and fast cooling rate during the welding process. The tensile strength of the welds was higher than that of TA15 alloy because of the fully B2 microstructure in the fusion zone, and the fracture preferentially occurred on the base metal of TA15 alloy during the tensile tests at room temperature and 650 °C.

Thomson scattering at general fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Young, W. C., E-mail: william.young@generalfusion.com; Parfeniuk, D.

2016-11-15

This paper provides an overview of the Thomson scattering diagnostic in use at General Fusion, including recent upgrades and upcoming plans. The plasma experiment under examination produces temperatures in the 50-500 eV range with density on the order of 10{sup 20} m{sup −3}. A four spatial point collection optics scheme has been implemented, with plans to expand to six spatial points. Recent changes to the optics of the laser beamline have reduced stray light. The system employs a frequency doubled Nd:YAG laser (532 nm), a grating spectrometer, and a photomultiplier array based detector.

The effects of short pulse laser surface cleaning on porosity formation and reduction in laser welding of aluminium alloy for automotive component manufacture

NASA Astrophysics Data System (ADS)

AlShaer, A. W.; Li, L.; Mistry, A.

2014-12-01

Laser welding of aluminium alloys typically results in porosity in the fusion zones, leading to poor mechanical and corrosion performances. Mechanical and chemical cleaning of surfaces has been used previously to remove contaminants for weld joint preparations. However, these methods are slow, ineffective (e.g. due to hydrogen trapping) or lead to environmental hazards. This paper reports the effects of short pulsed laser surface cleaning on porosity formation and reduction in laser welding of AC-170PX (AA6014) aluminium sheets (coated with Ti/Zr and lubricated using a dry lubricant AlO70) with two types of joints: fillet edge and flange couch, using an AA4043 filler wire for automotive component assembly. The effect of laser cleaning on porosity reduction during laser welding using a filler wire has not been reported before. In this work, porosity and weld fusion zone geometry were examined prior to and after laser cleaning. The nanosecond pulsed Nd:YAG laser cleaning was found to reduce porosity significantly in the weld fusion zones. For the fillet edge welds, porosity was reduced to less than 0.5% compared with 10-80% without laser cleaning. For flange couch welds, porosity was reduced to 0.23-0.8% with laser cleaning from 0.7% to 4.3% without laser cleaning. This has been found to be due to the elimination of contaminations and oxide layers that contribute to the porosity formation. The laser cleaning is based on thermal ablation. This research focuses on porosity reduction in laser welding of aluminium alloy. Weld quality was investigated for two joints, fillet edge and flange couch joints. The effect of laser cleaning on porosity reduction after welding was investigated. It was found that laser cleaning reduced porosity less than 1% in both joints. Weld dimensions and strength were evaluated and discussed for both types of joints.

Fusion Energy and Stopping Power in a Degenerate DT Pellet Driven by a Laser-Accelerated Proton Beam

NASA Astrophysics Data System (ADS)

Mehrangiz, M.; Ghasemizad, A.; Jafari, S.; Khanbabaei, B.

2016-06-01

In this paper, we have improved the fast ignition scheme in order to have more authority needed for high-energy-gain. Due to the more penetrability and energy deposition of the particle beams in fusion targets, we employ a laser-to-ion converter foil as a scheme for generating energetic ion beams to ignite the fusion fuel. We find the favorable intensity and wavelength of incident laser by evaluating the laser-proton conversion gain. By calculating the source-target distance, proton beam power and energy are estimated. Our analysis is generalized to the plasma degeneracy effects which can increase the fusion gain several orders of magnitude by decreasing the ion-electron collisions in the plasma. It is found that the wavelength of 0.53 μm and the intensity of about 1020 W/cm2, by saving about 10% conversion coefficient, are the suitable measured values for converting a laser into protons. Besides, stopping power and fusion burn calculations have been done in degenerate and non-degenerate plasma mediums. The results indicate that in the presence of degeneracy, the rate of fusion enhances. Supported by the Research Council of University of Guilan

Progress in Fast Ignition Studies with Electrons and Protons

NASA Astrophysics Data System (ADS)

MacKinnon, A. J.; Akli, K. U.; Bartal, T.; Beg, F. N.; Chawla, S.; Chen, C. D.; Chen, H.; Chen, S.; Chowdhury, E.; Fedosejevs, R.; Freeman, R. R.; Hey, D.; Higginson, D.; Key, M. H.; King, J. A.; Link, A.; Ma, T.; MacPhee, A. G.; Offermann, D.; Ovchinnikov, V.; Pasley, J.; Patel, P. K.; Ping, Y.; Schumacher, D. W.; Stephens, R. B.; Tsui, Y. Y.; Wei, M. S.; Van Woerkom, L. D.

2009-09-01

Isochoric heating of inertially confined fusion plasmas by laser driven MeV electrons or protons is an area of great topical interest in the inertial confinement fusion community, particularly with respect to the fast ignition (FI) concept for initiating burn in a fusion capsule. In order to investigate critical aspects needed for a FI point design, experiments were performed to study 1) laser-to-electrons or protons conversion issues and 2) laser-cone interactions including prepulse effects. A large suite of diagnostics was utilized to study these important parameters. Using cone—wire surrogate targets it is found that pre-pulse levels on medium scale lasers such as Titan at Lawrence Livermore National Laboratory produce long scale length plasmas that strongly effect coupling of the laser to FI relevant electrons inside cones. The cone wall thickness also affects coupling to the wire. Conversion efficiency to protons has also been measured and modeled as a function of target thickness, material. Conclusions from the proton and electron source experiments will be presented. Recent advances in modeling electron transport and innovative target designs for reducing igniter energy and increasing gain curves will also be discussed. In conclusion, a program of study will be presented based on understanding the fundamental physics of the electron or proton source relevant to FI.

Avalanche boron fusion by laser picosecond block ignition with magnetic trapping for clean and economic reactor

DOE PAGES

Hora, H.; Korn, G.; Eliezer, S.; ...

2016-10-11

Measured highly elevated gains of proton–boron (HB11) fusion (Picciottoet al., Phys. Rev. X4, 031030 (2014)) confirmed the exceptional avalanche reaction process (Lalousiset al., Laser Part. Beams 32, 409 (2014); Horaet al., Laser Part. Beams33, 607 (2015)) for the combination of the non-thermal block ignition using ultrahigh intensity laser pulses of picoseconds duration. The ultrahigh accelerationabovemore » $$10^{20}~\\text{cm}~\\text{s}^{-2}$$ for plasma blocks was theoretically and numerically predicted since 1978 (Hora,Physics of Laser Driven Plasmas(Wiley, 1981), pp. 178 and 179) and measured (Sauerbrey, Phys. Plasmas3, 4712 (1996)) in exact agreement (Horaet al., Phys. Plasmas14, 072701 (2007)) when the dominating force was overcoming thermal processes. This is based on Maxwell’s stress tensor by the dielectric properties of plasma leading to the nonlinear (ponderomotive) force $$f_{\\text{NL}}$$ resulting in ultra-fast expanding plasma blocks by a dielectric explosion. Combining this with measured ultrahigh magnetic fields and the avalanche process opens an option for an environmentally absolute clean and economic boron fusion power reactor. Finally, this is supported also by other experiments with very high HB11 reactions under different conditions (Labauneet al., Nature Commun.4, 2506 (2013)).« less

Conceptual design of laser fusion reactor KOYO-fast Concepts of reactor system and laser driver

NASA Astrophysics Data System (ADS)

Kozaki, Y.; Miyanaga, N.; Norimatsu, T.; Soman, Y.; Hayashi, T.; Furukawa, H.; Nakatsuka, M.; Yoshida, K.; Nakano, H.; Kubomura, H.; Kawashima, T.; Nishimae, J.; Suzuki, Y.; Tsuchiya, N.; Kanabe, T.; Jitsuno, T.; Fujita, H.; Kawanaka, J.; Tsubakimoto, K.; Fujimoto, Y.; Lu, J.; Matsuoka, S.; Ikegawa, T.; Owadano, Y.; Ueda, K.; Tomabechi, K.; Reactor Design Committee in Ife Forum, Members Of

2006-06-01

We have carried out the design studies of KOYO-Fast laser fusion power plant, using fast ignition cone targets, DPSSL lasers, and LiPb liquid wall chambers. Using fast ignition targets, we could design a middle sized 300 MWe reactor module, with 200 MJ fusion pulse energy and 4 Hz rep-rates, and 1200MWe modular power plants with 4 reactor modules and a 16 Hz laser driver. The liquid wall chambers with free surface cascade flows are proposed for cooling surface quickly enough to a 4 Hz pulse operation. We examined the potential of Yb-YAG ceramic lasers operated at 150˜ 225 K for both implosion and heating laser systems required for a 16-Hz repetition and 8 % total efficiency.

Evaluation of laser-driven ion energies for fusion fast-ignition research

NASA Astrophysics Data System (ADS)

Tosaki, S.; Yogo, A.; Koga, K.; Okamoto, K.; Shokita, S.; Morace, A.; Arikawa, Y.; Fujioka, S.; Nakai, M.; Shiraga, H.; Azechi, H.; Nishimura, H.

2017-10-01

We investigate laser-driven ion acceleration using kJ-class picosecond (ps) laser pulses as a fundamental study for ion-assisted fusion fast ignition, using a newly developed Thomson-parabola ion spectrometer (TPIS). The TPIS has a space- and weight-saving design, considering its use in an laser-irradiation chamber in which 12 beams of fuel implosion laser are incident, and, at the same time, demonstrates sufficient performance with its detectable range and resolution of the ion energy required for fast-ignition research. As a fundamental study on laser-ion acceleration using a ps pulse laser, we show proton acceleration up to 40 MeV at 1 × 10^{19} W cm^{-2}. The energy conversion efficiency from the incident laser into protons higher than 6 MeV is 4.6%, which encourages the realization of fusion fast ignition by laser-driven ions.

Angle Measurement of Objects outside the Linear Field of View of a Strapdown Semi-Active Laser Seeker.

PubMed

Zheng, Yongbin; Chen, Huimin; Zhou, Zongtan

2018-05-23

The accurate angle measurement of objects outside the linear field of view (FOV) is a challenging task for a strapdown semi-active laser seeker and is not yet well resolved. Considering the fact that the strapdown semi-active laser seeker is equipped with GPS and an inertial navigation system (INS) on a missile, in this work, we present an angle measurement method based on the fusion of the seeker’s data and GPS and INS data for a strapdown semi-active laser seeker. When an object is in the nonlinear FOV or outside the FOV, by solving the problems of space consistency and time consistency, the pitch angle and yaw angle of the object can be calculated via the fusion of the last valid angles measured by the seeker and the corresponding GPS and INS data. The numerical simulation results demonstrate the correctness and effectiveness of the proposed method.

Fusion technologies for Laser Inertial Fusion Energy (LIFE)

NASA Astrophysics Data System (ADS)

Kramer, K. J.; Latkowski, J. F.; Abbott, R. P.; Anklam, T. P.; Dunne, A. M.; El-Dasher, B. S.; Flowers, D. L.; Fluss, M. J.; Lafuente, A.; Loosmore, G. A.; Morris, K. R.; Moses, E.; Reyes, S.

2013-11-01

The Laser Inertial Fusion-based Energy (LIFE) engine design builds upon on going progress at the National Ignition Facility (NIF) and offers a near-term pathway to commercial fusion. Fusion technologies that are critical to success are reflected in the design of the first wall, blanket and tritium separation subsystems. The present work describes the LIFE engine-related components and technologies. LIFE utilizes a thermally robust indirect-drive target and a chamber fill gas. Coolant selection and a large chamber solid-angle coverage provide ample tritium breeding margin and high blanket gain. Target material selection eliminates the need for aggressive chamber clearing, while enabling recycling. Demonstrated tritium separation and storage technologies limit the site tritium inventory to attractive levels. These key technologies, along with the maintenance and advanced materials qualification program have been integrated into the LIFE delivery plan. This describes the development of components and subsystems, through prototyping and integration into a First Of A Kind power plant. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Infrared Smartt Interferometer As An Alignment Tool For Carbon Dioxide Laser Fusion Systems

NASA Astrophysics Data System (ADS)

Viswanathan, V. K.; Bolen, P. D.

1980-11-01

It is essential to minimize the pointing and focusing errors at the focal plane for many applications involving infrared laser systems. In the case of the LASL CO2 laser fusion systems, with two beams in the Gemini System and eight beams in the Helios System, this is particularly important. The LASL Helios CO2 Laser Fusion System has eight 34-cm diameter beams emerging from the power amplifier and each beam is brought to focus by an off-aperture parabola (nearly 77.3-cm focal length) resulting in a nearly F/2.4 beam at the focal plane. The design tolerance at the focal plane for pointing accuracy is +/- 25 microns and for focusing accuracy is +/- 50 microns for this system. This paper describes an alignment scheme based on the use of the infrared Smartt interferometer' and compares the results obtained using this technique and the autocollimating Hartmann scheme2 in a laboratory setup duplicating the target chamber region of one of the beams of the Helios System. The results using the Smartt interferometer show that pointing accuracy of +/- 12.5 microns and focusing accuracies of ± 15 microns are obtained at the focal plane of the system.

Benefits of Moderate-Z Ablators for Direct-Drive Inertial Confinement Fusion

NASA Astrophysics Data System (ADS)

Lafon, M.; Betti, R.; Anderson, K. S.; Collins, T. J. B.; Skupsky, S.; McKenty, P. W.

2014-10-01

Control of hydrodynamic instabilities and DT-fuel preheating by hot electrons produced by laser-plasma interaction is crucial in inertial confinement fusion. Moderate- Z ablators have been shown to reduce the laser imprinting on target and suppress the generation of hot electrons from the two-plasmon-decay instability. These results have motivated the use of ablators of higher- Z than pure plastic in direct-drive-ignition target designs for the National Ignition Facility (NIF). Two-dimensional radiation-hydrodynamic simulations assess the robustness of these ignition designs to laser imprint and capsule nonuniformities. The complex behavior of the hydrodynamic stability of mid- Z ablators is investigated through single and multimode simulations. A polar-drive configuration is developed within the NIF Laser System specifications for each ablator material. The use of multilayer ablators is also investigated to enhance the hydrodynamic stability. Results indicate that ignition target designs using mid- Z ablators exhibit good hydrodynamic properties, leading to high target gain for direct-drive implosions on the NIF. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944 and the Office of Fusion Energy Sciences Number DE-FG02-04ER54786.

Soft x-ray streak camera for laser fusion applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stradling, G.L.

This thesis reviews the development and significance of the soft x-ray streak camera (SXRSC) in the context of inertial confinement fusion energy development. A brief introduction of laser fusion and laser fusion diagnostics is presented. The need for a soft x-ray streak camera as a laser fusion diagnostic is shown. Basic x-ray streak camera characteristics, design, and operation are reviewed. The SXRSC design criteria, the requirement for a subkilovolt x-ray transmitting window, and the resulting camera design are explained. Theory and design of reflector-filter pair combinations for three subkilovolt channels centered at 220 eV, 460 eV, and 620 eV aremore » also presented. Calibration experiments are explained and data showing a dynamic range of 1000 and a sweep speed of 134 psec/mm are presented. Sensitivity modifications to the soft x-ray streak camera for a high-power target shot are described. A preliminary investigation, using a stepped cathode, of the thickness dependence of the gold photocathode response is discussed. Data from a typical Argus laser gold-disk target experiment are shown.« less

Effect of laser welding parameters on the austenite and martensite phase fractions of NiTi

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oliveira, J.P., E-mail: jp.oliveira@campus.fct.unl

Although laser welding is probably the most used joining technique for NiTi shape memory alloys there is still a lack of understanding about the effects of laser welding parameters on the microstructural induced changes: in both the heat affected and fusion zones martensite may be present, while the base material is fully austenitic. Synchrotron X-ray diffraction was used for fine probing laser welded NiTi joints. Through Rietveld refinement the martensite and austenite phase fractions were determined and it was observed that the martensite content increases towards the weld centreline. This is related to a change of the local transformation temperaturesmore » on these regions, which occurs due to compositional variation in those regions. The martensite phase fraction in the thermally affected regions may have significant implications on functional properties on these joints. - Highlights: •Synchrotron X-ray diffraction was used for fine probing of the microstructure in laser welded NiTi joints. •Rietveld refinement allowed to determine the content of martensite along the heat affected and fusion zones. •The martensite content increases from the base material towards the weld centreline.« less

Fluid mechanics of fusion lasers. Final report, September 11, 1978-June 5, 1980

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shwartz, J; Kulkarny, V A; Ausherman, D A

1980-01-01

Flow loop components required to operate continuous-flow, repetitively-pulsed CO/sub 2/ and KrF laser drivers for ICF were identified and their performance requirements were specified. It was found that the laser flow loops can have a major effect on the laser beam quality and overall efficiency. The pressure wave suppressor was identified as the most critical flow loop component. The performance of vented side-wall suppressors was evaluated both analytically and experimentally and found capable of meeting the performance requirements of the CO/sub 2/ and KrF fusion lasers. All other laser flow loop components are essentially similar to those used in conventional,more » low speed wind tunnels and are therefore well characterized and can be readily incorporated into fusion laser flow systems designs.« less

Rapid heating of matter using high power lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bang, Woosuk

2016-04-08

This slide presentation describes motivation (uniform and rapid heating of a target, opportunity to study warm dense matter, study of nuclear fusion reactions), rapid heating of matter with intense laser-driven ion beams, visualization of the expanding warm dense gold and diamond, and nuclear fusion experiments using high power lasers (direct heating of deuterium spheres (radius ~ 10nm) with an intense laser pulse.

Analysis of laser-induction hybrid cladding processing conditions

NASA Astrophysics Data System (ADS)

Huang, Yongjun; Zeng, Xiaoyan; Hu, Qianwu

2007-12-01

A new cladding approach based on laser-induction hybrid technique on flat sheets is presented in this paper. Coating is produced by means of 5kw cw CO II laser equipped with 100kw high frequent inductor, and the experiments set-up, involving a special machining-head, which can provide laser-induction hybrid heat resources simultaneously. The formation of thick NiCrSiB coating on a steel substrate by off-axial powder feeding is studied from an experimental point of view. A substrate melting energy model is developed to describe the energy relationship between laser-induction hybrid cladding and laser cladding alone quantitatively. By comparing the experimental results with the calculational ones, it is shown that the tendency of fusion zone height of theoretical calculation is in agreement with that of tests in laser-induction hybrid cladding. Via analyses and tests, the conclusions can be lead to that the fusion zone height can be increased easily and the good bond of cladding track can be achieved within wide cladding processing window in laser-induction hybrid processing. It shows that the induction heating has an obvious effect on substrate melting and metallurgical bond.

Cross-Beam Energy Transfer Driven by Incoherent Laser Beams with Frequency Detuning

NASA Astrophysics Data System (ADS)

Maximov, A.; Myatt, J. F.; Short, R. W.; Igumenshchev, I. V.; Seka, W.

2015-11-01

In the direct-drive method of the inertial confinement fusion (ICF), the coupling of laser energy to target plasmas is strongly influenced by the effect of cross-beam energy transfer (CBET) between multiple driving laser beams. The laser -plasma interaction (LPI) model of CBET is based on the nonparaxial laser light propagation coupled with the low-frequency ion-acoustic-domain plasma response. Common ion waves driven by multiple laser beams play a very important role in CBET. The effect of the frequency detuning (colors) in the driving laser beams is studied and it is shown to significantly reduce the level of common ion waves and therefore the level of CBET. The differences between the LPI-based CBET model and the ray-based CBET model used in hydrocodes are discussed. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

Progress in the Science and Technology of Direct Drive Laser Fusion with the KrF Laser

DTIC Science & Technology

2010-12-01

important parameters KrF technology leads) Direct Laser Drive is a better choice for Energy Indirect Drive (initial path for NIF ) Laser Beams x-rays Hohlraum...Pellet Direct Drive (IFE) Laser Beams Pellet .. • ID Ignition being explored on NIF • Providing high enough gain for pure fusion energy is...challenging. • DD Ignition physics can be explored on NIF . • More efficient use of laser light, and greater flexibility in applying drive provides potential for

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Physics of the plasma corona in the problem of laser controlled thermonuclear fusion

NASA Astrophysics Data System (ADS)

Andreev, N. E.; Gorbunov, Leonid M.; Tikhonchuk, Vladimir T.

1994-09-01

A brief analysis is made of the most important nonlinear processes which result from the interaction of laser radiation with thermonuclear targets. lt is shown that problems in the physics of the plasma corona should be an essential part of any programme of research on laser controlled thermonuclear fusion. A list is given of the problems that have to be solved first before going to the next level of laser energies.

Some recent studies on laser cladding and dissimilar welding

NASA Astrophysics Data System (ADS)

Kaul, Rakesh; Ganesh, P.; Paul, C. P.; Albert, S. K.; Mudali, U. Kamachi; Nath, A. K.

2006-01-01

Indigenous development of high power CO II laser technology and industrial application of lasers represent two important mandates of the laser program, being pursued at Centre for Advanced Technology (CAT), India. The present paper describes some of the important laser material processing studies, involving cladding and dissimilar welding, performed in authors' laboratory. The first case study describes how low heat input characteristics of laser cladding process has been successfully exploited for suppressing dilution in "Colmonoy6" (a nickel-base hardfacing alloy) deposits on austenitic stainless steel components. Crack free hardfaced deposits were obtained by controlling heating and cooling rates associated with laser treatment. The results show significant advantage over Colmonoy 6 deposits made by GTAW, where a 2.5 mm thick region of dilution (with reduced hardness) develops next to substrateiclad interface. The next work involves laser-assisted deposition of graded "Stellite6" (a Co-base hardfacing alloy) with smooth transition in chemical composition and hardness for enhanced resistance against cracking, esp. under thermal cycling conditions. The following two case studies demonstrate significant improvement in corrosion properties of type 304L stainless steel by laser surface alloying, achieved through cladding route. The following case study demonstrates engineering of fusion zone microstructure of end plug dissimilar weld (between alloy D9 and type 3 16M stainless steel) by controlled preferential displacement of focused laser beam, which, in-turn, enhanced its resistance against solidification cracking. Crater appearing at the termination point of laser weld is also eliminated by ramping of laser power towards the end of laser welding. The last case study involves engineering of fusion zone microstructure of dissimilar laser weld between type 304 austenitic stainless steel and stabilized 17%Cr ferritic stainless steel by controlling welding parameters.

Optical coatings for laser fusion applications

NASA Astrophysics Data System (ADS)

Lowdermilk, W. H.; Milam, D.; Rainer, F.

1980-04-01

Lasers for fusion experiments use thin-film dielectric coatings for reflecting antireflecting and polarizing surface elements. Coatings are most important to the Nd:glass laser application. The most important requirements of these coatings are accuracy of the average value of reflectance and transmission, uniformity of amplitude and phase front of the reflected or transmitted light, and laser damage threshold. Damage resistance strongly affects the laser's design and performance. The success of advanced lasers for future experiments and for reactor applications requires significant developments in damage resistant coatings for ultraviolet laser radiation.

Gaussian process-based surrogate modeling framework for process planning in laser powder-bed fusion additive manufacturing of 316L stainless steel

DOE PAGES

Tapia, Gustavo; Khairallah, Saad A.; Matthews, Manyalibo J.; ...

2017-09-22

Here, Laser Powder-Bed Fusion (L-PBF) metal-based additive manufacturing (AM) is complex and not fully understood. Successful processing for one material, might not necessarily apply to a different material. This paper describes a workflow process that aims at creating a material data sheet standard that describes regimes where the process can be expected to be robust. The procedure consists of building a Gaussian process-based surrogate model of the L-PBF process that predicts melt pool depth in single-track experiments given a laser power, scan speed, and laser beam size combination. The predictions are then mapped onto a power versus scan speed diagrammore » delimiting the conduction from the keyhole melting controlled regimes. This statistical framework is shown to be robust even for cases where experimental training data might be suboptimal in quality, if appropriate physics-based filters are applied. Additionally, it is demonstrated that a high-fidelity simulation model of L-PBF can equally be successfully used for building a surrogate model, which is beneficial since simulations are getting more efficient and are more practical to study the response of different materials, than to re-tool an AM machine for new material powder.« less

Gaussian process-based surrogate modeling framework for process planning in laser powder-bed fusion additive manufacturing of 316L stainless steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tapia, Gustavo; Khairallah, Saad A.; Matthews, Manyalibo J.

Here, Laser Powder-Bed Fusion (L-PBF) metal-based additive manufacturing (AM) is complex and not fully understood. Successful processing for one material, might not necessarily apply to a different material. This paper describes a workflow process that aims at creating a material data sheet standard that describes regimes where the process can be expected to be robust. The procedure consists of building a Gaussian process-based surrogate model of the L-PBF process that predicts melt pool depth in single-track experiments given a laser power, scan speed, and laser beam size combination. The predictions are then mapped onto a power versus scan speed diagrammore » delimiting the conduction from the keyhole melting controlled regimes. This statistical framework is shown to be robust even for cases where experimental training data might be suboptimal in quality, if appropriate physics-based filters are applied. Additionally, it is demonstrated that a high-fidelity simulation model of L-PBF can equally be successfully used for building a surrogate model, which is beneficial since simulations are getting more efficient and are more practical to study the response of different materials, than to re-tool an AM machine for new material powder.« less

Direct-drive inertial confinement fusion research at the Laboratory for Laser Energetics: charting the path to thermonuclear ignition

NASA Astrophysics Data System (ADS)

McCrory, R. L.; Regan, S. P.; Loucks, S. J.; Meyerhofer, D. D.; Skupsky, S.; Betti, R.; Boehly, T. R.; Craxton, R. S.; Collins, T. J. B.; Delettrez, J. A.; Edgell, D.; Epstein, R.; Fletcher, K. A.; Freeman, C.; Frenje, J. A.; Glebov, V. Yu.; Goncharov, V. N.; Harding, D. R.; Igumenshchev, I. V.; Keck, R. L.; Kilkenny, J. D.; Knauer, J. P.; Li, C. K.; Marciante, J.; Marozas, J. A.; Marshall, F. J.; Maximov, A. V.; McKenty, P. W.; Myatt, J.; Padalino, S.; Petrasso, R. D.; Radha, P. B.; Sangster, T. C.; Séguin, F. H.; Seka, W.; Smalyuk, V. A.; Soures, J. M.; Stoeckl, C.; Yaakobi, B.; Zuegel, J. D.

2005-10-01

Significant theoretical and experimental progress continues to be made at the University of Rochester's Laboratory for Laser Energetics (LLE), charting the path to direct-drive inertial confinement fusion (ICF) ignition. Direct drive offers the potential for higher-gain implosions than x-ray drive and is a leading candidate for an inertial fusion energy power plant. LLE's direct-drive ICF ignition target designs for the National Ignition Facility (NIF) are based on hot-spot ignition. A cryogenic target with a spherical DT-ice layer, within or without a foam matrix, enclosed by a thin plastic shell, will be directly irradiated with ~1.5 MJ of laser energy. Cryogenic and plastic/foam (surrogate-cryogenic) targets that are hydrodynamically scaled from these ignition target designs are imploded on the 60-beam, 30 kJ, UV OMEGA laser system to validate the key target physics issues, including energy coupling, hydrodynamic instabilities and implosion symmetry. Prospects for direct-drive ignition on the NIF are extremely favourable, even while it is in its x-ray-drive irradiation configuration, with the development of the polar-direct-drive concept. A high-energy petawatt capability is being constructed at LLE next to the existing 60-beam OMEGA compression facility. This OMEGA EP (extended performance) laser will add two short-pulse, 2.6 kJ beams to the OMEGA laser system to backlight direct-drive ICF implosions and study fast-ignition physics with focused intensities up to 6 × 1020 W cm-2.

Minimizing scatter-losses during pre-heat for magneto-inertial fusion targets

NASA Astrophysics Data System (ADS)

Geissel, Matthias; Harvey-Thompson, Adam J.; Awe, Thomas J.; Bliss, David E.; Glinsky, Michael E.; Gomez, Matthew R.; Harding, Eric; Hansen, Stephanie B.; Jennings, Christopher; Kimmel, Mark W.; Knapp, Patrick; Lewis, Sean M.; Peterson, Kyle; Schollmeier, Marius; Schwarz, Jens; Shores, Jonathon E.; Slutz, Stephen A.; Sinars, Daniel B.; Smith, Ian C.; Speas, C. Shane; Vesey, Roger A.; Weis, Matthew R.; Porter, John L.

2018-02-01

The size, temporal and spatial shape, and energy content of a laser pulse for the pre-heat phase of magneto-inertial fusion affect the ability to penetrate the window of the laser-entrance-hole and to heat the fuel behind it. High laser intensities and dense targets are subject to laser-plasma-instabilities (LPI), which can lead to an effective loss of pre-heat energy or to pronounced heating of areas that should stay unexposed. While this problem has been the subject of many studies over the last decades, the investigated parameters were typically geared towards traditional laser driven Inertial Confinement Fusion (ICF) with densities either at 10% and above or at 1% and below the laser's critical density, electron temperatures of 3-5 keV, and laser powers near (or in excess of) 1 × 1015 W/cm2. In contrast, Magnetized Liner Inertial Fusion (MagLIF) [Slutz et al., Phys. Plasmas 17, 056303 (2010) and Slutz and Vesey, Phys. Rev. Lett. 108, 025003 (2012)] currently operates at 5% of the laser's critical density using much thicker windows (1.5-3.5 μm) than the sub-micron thick windows of traditional ICF hohlraum targets. This article describes the Pecos target area at Sandia National Laboratories using the Z-Beamlet Laser Facility [Rambo et al., Appl. Opt. 44(12), 2421 (2005)] as a platform to study laser induced pre-heat for magneto-inertial fusion targets, and the related progress for Sandia's MagLIF program. Forward and backward scattered light were measured and minimized at larger spatial scales with lower densities, temperatures, and powers compared to LPI studies available in literature.

Beyond the random phase approximation: Stimulated Brillouin backscatter for finite laser coherence times

DOE Office of Scientific and Technical Information (OSTI.GOV)

Korotkevich, Alexander O.; Lushnikov, Pavel M., E-mail: plushnik@math.unm.edu; Landau Institute for Theoretical Physics, 2 Kosygin Str., Moscow 119334

2015-01-15

We developed a linear theory of backward stimulated Brillouin scatter (BSBS) of a spatially and temporally random laser beam relevant for laser fusion. Our analysis reveals a new collective regime of BSBS (CBSBS). Its intensity threshold is controlled by diffraction, once cT{sub c} exceeds a laser speckle length, with T{sub c} the laser coherence time. The BSBS spatial gain rate is approximately the sum of that due to CBSBS, and a part which is independent of diffraction and varies linearly with T{sub c}. The CBSBS spatial gain rate may be reduced significantly by the temporal bandwidth of KrF-based laser systemsmore » compared to the bandwidth currently available to temporally smoothed glass-based laser systems.« less

Investigation of Laser Based Thomson Scattering

DTIC Science & Technology

2015-06-04

laser liquid interaction has the potential to provide sources of energetic ions and fission products such as neutrons . The development of strong...by the production of heavy water d-d fusion and the production of neutrons . Finally, in section VII the tight focusing of light by a 2π mirror is...laser system is estimated to be 10 -15 , using cross- polarization modulation and two plasma mirrors. These parameters allow prepulse expansion to be

Effect of equation of state on laser imprinting by comparing diamond and polystyrene foils

NASA Astrophysics Data System (ADS)

Kato, H.; Shigemori, K.; Nagatomo, H.; Nakai, M.; Sakaiya, T.; Ueda, T.; Terasaki, H.; Hironaka, Y.; Shimizu, K.; Azechi, H.

2018-03-01

We present herein a comprehensive study of how the equation of state affects laser imprinting by nonuniform laser irradiation of an inertial fusion target. It has been suggested that a stiffer and denser material would reduce laser imprinting based on the equation of motion with pressure perturbation. We examine the detailed temporal evolution of the imprint amplitude by using the two-dimensional radiation hydrodynamic simulation PINOCO-2D for diamond, which is a candidate stiff-ablator material for inertial fusion targets. The simulated laser imprinting amplitude is compared with experimental measurements of areal-density perturbations obtained by using face-on x-ray backlighting for diamond and polystyrene (PS) (the latter as a reference). The experimental results are well reproduced by the results of the PINOCO-2D simulation, which indicates that the imprinting amplitude due to nonuniform irradiation (average intensity, 4.0 × 1012 to 5.0 × 1013) differs by a factor of two to three between diamond and PS. The difference in laser imprinting is mainly related to the material density and compressibility. These parameters are key factors that determine the laser imprinting amplitude.

PREFACE: The fifth International Conference on Inertial Fusion Sciences and Applications (IFSA2007)

NASA Astrophysics Data System (ADS)

Azechi, Hiroshi; Hammel, Bruce; Gauthier, Jean-Claude

2008-06-01

The Fifth International Conference on Inertial Fusion Sciences and Applications (IFSA 2007) was held on 9-14 September 2007 at Kobe International Conference Center in Kobe, Japan. The host organizations for this conference were Osaka University and the Institute of Laser Engineering (ILE) at Osaka University; and co-organized by the Institute Lasers and Plasmas (ILP) in France, the Commissariatá l'Energie Atomique (CEA), Lawrence Livermore National Laboratory (LLNL), National Institute for Fusion Science (NIFS) in Japan, and Kansai Photon Science Institute (KPSI), Japan Atomic Energy Agency (JAEA). The conference objective was to review the state of the art of research in inertial fusion sciences and applications since the last conference held in Biarritz, France, in 2005. 470 abstracts were accepted, and 448 persons from 18 countries attended the conference. These Proceedings contain 287 of the papers presented at IFSA 2007. This collection of papers represents the manuscripts submitted to and passing the peer review process. The program was organized with some specific features: The reviews of influential programs appeared both at the very beginning and at the very end of the Conference to attract attendance throughout the Conference. Each poster session had the same time period as a single oral session, thereby avoiding overlap with oral talks. The everyday program was structured to be as similar as possible so the attendees could easily recognize the program. With a goal of achieving inertial fusion ignition and burn propagation in the laboratory, researchers presented the exciting advances in both traditional hot spot ignition and fast ignition approach, including status report of USA's National Ignition Facility (NIF), French Laser Magajoule (LMJ), Japanese Fast Ignition Realization Experiment (FIREX), and European High Power laser Energy Research (HiPER). A particular emphasis of the meeting was that the `physics of inertial fusion' category was dominated by fast-ignition and related ultra-intense laser interaction. Progress in direct drive over the past few years resulted in the achievement of high-density cryogenic implosions at OMEGA. Continuous progresses in hohlraum physics gave confidence in the achievement of ignition at NIF and LMJ. Advances in Z-pinch included double-hohlraum irradiation symmetry and the PW laser beam for the Z-facility. Progress of laser material development for IFE driver was a very interesting topic of inertial fusion energy drivers, including KrF and DPSSL lasers and particle beams. Of special interest, a future session was focused on strategy of inertial fusion energy development. Laboratory tours were held in the middle of the Conference. The Laser for Fusion EXperiments (LFEX), a new high-energy petawatt laser at ILE, was one of the key attractions of IFSA 2007. 83 participants toured LFEX and GEKKO XII lasers, and 35 joined a tour of KPSA-JAEA. In parallel to the tour, the `Symposium on Academics-Industries Cooperation for Applications of High-Power Lasers' was held with more than 90 participants mostly from the industrial community. These Proceedings start with special chapters on the keynote and focus speeches and the Teller lectures. The keynotes and focus give an overview of progress in inertial fusion in Asia, North America, and Europe. The Teller lectures show the contributions of this year's two winners: Brian Thomas of AWE, UK and Kunioki Mima of ILE. The remainder of the Proceedings is divided into three parts. Part A covers the physics of inertial fusion; Part B covers laser, particle beams, and fusion technology including IFE reactors and target fabrication; and Part C covers science and technology applications such as laboratory astrophysics, laser particle acceleration, x-ray and EUV sources, and new applications of intense lasers. These parts are further divided into chapters covering specific areas of science or technology. Within each chapter the talks relevant to that subject are gathered. The IFSA International Organizing Committee and Scientific Advisory Board appreciate the efforts of inertial fusion researchers worldwide in making IFSA 2007 an extremely successful conference. The proceedings were published with the support of Dr Y Sakawa, Dr H Homma, Ms S Karasuyama, Ms M Odagiri, and Ms I Kobatake. Kunioki Mima Co-chair Hiroshi Azechi Technical Program Committee Co-chair John Lindl Co-chair Bruce Hammel Technical Program Committee Co-chair Christine Labaune Co-chair Jean-Claude Gauthier Technical Program Committee Co-chair

Femtosecond laser surgery of two-cell mouse embryos: effect on viability, development, and tetraploidization

NASA Astrophysics Data System (ADS)

Osychenko, Alina A.; Zalessky, Alexandr D.; Kostrov, Andrey N.; Ryabova, Anastasia V.; Krivokharchenko, Alexander S.; Nadtochenko, Viktor A.

2017-12-01

The effect of the laser pulse energy and total expose of the energy incident on the embryo blastomere fusion probability was investigated. The probability of the four different events after laser pulse was determined: the fusion of two blastomeres with the following formation of tetraploid embryo, the destruction of the first blastomere occurs, the second blastomere conservation remains intact, the destruction and the death of both cells; two blastomeres were not fused, and no morphological changes occurred. We report on viability and quality of the embryo after laser surgery as a function of the laser energy incident. To characterize embryo quality, the probability of the blastocyst stage achievement was estimated and the blastocyst cells number was calculated. Blastocoel formation is the only event of morphogenesis in the preimplantation development of mammals, so we assumed it as an indicator of the time of embryonic "clocks" and observed it among fused and control embryos. The blastocoel formation time is the same for fused and control embryos. It indicates that embryo clocks were not affected due to blastomere fusion. Thus, the analysis of the fluorescence microscopic images of nuclei in the fused embryo revealed that nuclei fusion does not occur after blastomere fusion.

Laser Induced Nuclear Fusion, LINF, In Muonic Molecules With Ultrashort Super Intense Laser Fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bandrauk, Andre D.; Paramonov, Gennady K.

2010-02-02

Muonium molecules where muons replace electrons increase the stability of molecules to ionization at superhigh intensities, I>10{sup 20} W/cm{sup 2}. We show furthermore from numerical simulations that in the nonsymmetric series, pdu, dtu, ptu, the permanent dipole moments can be used to enhance LINF, Laser Induced Nuclear Fusion by laser induced recollision of the light nucleus with the heavier nucleus.

Application of Laser Treatment for Hardening Parts of Gas Turbine Engines from Titanium Alloys

NASA Astrophysics Data System (ADS)

Girzhon, V. V.; Ovchinnikov, A. V.

2017-03-01

X-ray diffraction analysis and light microscopy are used to study the structure of surface layers of helically extruded specimens of titanium alloy VT25U after laser fusion of the surface. It is shown that the rates of cooling of the melt promote formation of a martensitic α″-phase in the zone of laser fusion and of a submicrocrystalline microstructure. The microhardness in the zone of fusion of the initial specimens exceeds the microhardness of the specimens after the extrusion.

Laser fusion pulse shape controller

DOEpatents

Siebert, Larry D.

1977-01-01

An apparatus for controlling the pulse shape, i.e., the pulse duration and intensity pattern, of a pulsed laser system, and which is particularly well adapted for controlling the pellet ignition pulse in a laser-driven fusion reaction system. The apparatus comprises a laser generator for providing an optical control pulse of the shape desired, a pulsed laser triggered by the control pulse, and a plurality of optical Kerr-effect gates serially disposed at the output of the pulsed laser and selectively triggered by the control pulse to pass only a portion of the pulsed laser output generally corresponding in shape to the control pulse.

Fiber Laser Welded AZ31 Magnesium Alloy: The Effect of Welding Speed on Microstructure and Mechanical Properties

NASA Astrophysics Data System (ADS)

Chowdhury, S. H.; Chen, D. L.; Bhole, S. D.; Powidajko, E.; Weckman, D. C.; Zhou, Y.

2012-06-01

This study was aimed at characterizing microstructural change and evaluating tensile and fatigue properties of fiber laser welded AZ31B-H24 Mg alloy with special attention to the effect of welding speed. Laser welding led to the formation of equiaxed dendrites in the fusion zone and columnar dendrites near the fusion zone boundary along with divorced eutectic Mg17Al12 particles and recrystallized grains in the heat-affected zone. The lowest hardness across the weld appeared in the fusion zone. Although the yield strength, ductility, and fatigue life decreased, the hardening capacity increased after laser welding, with a joint efficiency reaching about 90 pct. A higher welding speed resulted in a narrower fusion zone, smaller grain size, higher yield strength, and longer fatigue life, as well as a slightly lower strain-hardening capacity mainly because of the smaller grain sizes. Tensile fracture occurred in the fusion zone, whereas fatigue failure appeared essentially in between the heat-affected zone and the fusion zone. Fatigue cracks initiated from the near-surface welding defects and propagated by the formation of fatigue striations together with secondary cracks.

New High Gain Target Design for a Laser Fusion Power Plant

DTIC Science & Technology

2000-06-07

target with a minimum energy gain, about 100. Demonstration of ignition or low gain is only important for fusion energy if it leads into a target concept...nonlinear saturation of these instabilities. Our approach is to try to avoid them. 4. A Development Path to Fusion Energy The laser and target concept...on the exact date required to develop fusion energy , it would be worthwhile for a power plant development program to provide enough time and funds

Considerations on the construction of a Powder Bed Fusion platform for Additive Manufacturing

NASA Astrophysics Data System (ADS)

Andersen, Sebastian Aagaard; Nielsen, Karl-Emil; Pedersen, David Bue; Nielsen, Jakob Skov

As the demand for moulds and other tools becomes increasingly specific and complex, an additive manufacturing approach to production is making its way to the industry through laser based consolidation of metal powder particles by a method known as powder bed fusion. This paper concerns a variety of design choices facilitating the development of an experimental powder bed fusion machine tool, capable of manufacturing metal parts with strength matching that of conventional manufactured parts and a complexity surpassing that of subtractive processes. To understand the different mechanisms acting within such an experimental machine tool, a fully open and customizable rig is constructed. Emphasizing modularity in the rig, allows alternation of lasers, scanner systems, optical elements, powder deposition, layer height, temperature, atmosphere, and powder type. Through a custom-made software platform, control of the process is achieved, which extends into a graphical user interface, easing adjustment of process parameters and the job file generation.

Inertial Confinement Fusion Annual Report 1997

DOE Office of Scientific and Technical Information (OSTI.GOV)

Correll, D

The ICF Annual Report provides documentation of the achievements of the LLNL ICF Program during the fiscal year by the use of two formats: (1) an Overview that is a narrative summary of important results for the fiscal year and (2) a compilation of the articles that previously appeared in the ICF Quarterly Report that year. Both the Overview and Quarterly Report are also on the Web at http://lasers.llnl.gov/lasers/pubs/icfq.html. Beginning in Fiscal Year 1997, the fourth quarter issue of the ICF Quarterly was no longer printed as a separate document but rather included in the ICF Annual. This change providedmore » a more efficient process of documenting our accomplishments with-out unnecessary duplication of printing. In addition we introduced a new document, the ICF Program Monthly Highlights. Starting with the September 1997 issue and each month following, the Monthly Highlights will provide a brief description of noteworthy activities of interest to our DOE sponsors and our stakeholders. The underlying theme for LLNL's ICF Program research continues to be defined within DOE's Defense Programs missions and goals. In support of these missions and goals, the ICF Program advances research and technology development in major interrelated areas that include fusion target theory and design, target fabrication, target experiments, and laser and optical science and technology. While in pursuit of its goal of demonstrating thermonuclear fusion ignition and energy gain in the laboratory, the ICF Program provides research and development opportunities in fundamental high-energy-density physics and supports the necessary research base for the possible long-term application of inertial fusion energy for civilian power production. ICF technologies continue to have spin-off applications for additional government and industrial use. In addition to these topics, the ICF Annual Report covers non-ICF funded, but related, laser research and development and associated applications. We also provide a short summary of the quarterly activities within Nova laser operations, Beamlet laser operations, and National Ignition Facility laser design. LLNL's ICF Program falls within DOE's national ICF program, which includes the Nova and Beamlet (LLNL), OMEGA (University of Rochester Laboratory for Laser Energetics), Nike (Naval Research Laboratory), and Trident (Los Alamos National Laboratory) laser facilities. The Particle Beam Fusion Accelerator (Z) and Saturn pulsed-power facilities are at Sandia National Laboratories. General Atomics, Inc., develops and provides many of the targets for the above experimental facilities. Many of the ICF Annual Report articles are co-authored with our colleagues from these other ICF institutions.« less

Soft X-ray streak camera for laser fusion applications

NASA Astrophysics Data System (ADS)

Stradling, G. L.

1981-04-01

The development and significance of the soft x-ray streak camera (SXRSC) in the context of inertial confinement fusion energy development is reviewed as well as laser fusion and laser fusion diagnostics. The SXRSC design criteria, the requirement for a subkilovolt x-ray transmitting window, and the resulting camera design are explained. Theory and design of reflector-filter pair combinations for three subkilovolt channels centered at 220 eV, 460 eV, and 620 eV are also presented. Calibration experiments are explained and data showing a dynamic range of 1000 and a sweep speed of 134 psec/mm are presented. Sensitivity modifications to the soft x-ray streak camera for a high-power target shot are described. A preliminary investigation, using a stepped cathode, of the thickness dependence of the gold photocathode response is discussed. Data from a typical Argus laser gold-disk target experiment are shown.

Next-generation laser for inertial confinement fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marshall, C; Bibeau, C; Bayramian, A

1998-03-13

We are developing and building the ''Mercury'' laser system as the first in a series of a new generation of diode-pumped solid-state lasers (DPSSL) for advanced high energy density (HED) physics experiments at LLNL. Mercury will be the first integrated demonstration of a scalable laser architecture compatible with advanced Inertial Confinement Fusion (ICF) goals. Primary performance goals include 10% efficiencies at 10 Hz and a <10 ns pulse with l {omega} energies of 100 J and with 2 {omega}/3 {omega} frequency conversion. Achieving this performance will provide a near term capability for HED experiments and prove the potential of DPSSLsmore » for inertial fusion energy (IFE).« less

Remotely controlled fusion of selected vesicles and living cells: a key issue review

NASA Astrophysics Data System (ADS)

Bahadori, Azra; Moreno-Pescador, Guillermo; Oddershede, Lene B.; Bendix, Poul M.

2018-03-01

Remote control over fusion of single cells and vesicles has a great potential in biological and chemical research allowing both transfer of genetic material between cells and transfer of molecular content between vesicles. Membrane fusion is a critical process in biology that facilitates molecular transport and mixing of cellular cytoplasms with potential formation of hybrid cells. Cells precisely regulate internal membrane fusions with the aid of specialized fusion complexes that physically provide the energy necessary for mediating fusion. Physical factors like membrane curvature, tension and temperature, affect biological membrane fusion by lowering the associated energy barrier. This has inspired the development of physical approaches to harness the fusion process at a single cell level by using remotely controlled electromagnetic fields to trigger membrane fusion. Here, we critically review various approaches, based on lasers or electric pulses, to control fusion between individual cells or between individual lipid vesicles and discuss their potential and limitations for present and future applications within biochemistry, biology and soft matter.

Fast heating of ultrahigh-density plasma as a step towards laser fusion ignition.

PubMed

Kodama, R; Norreys, P A; Mima, K; Dangor, A E; Evans, R G; Fujita, H; Kitagawa, Y; Krushelnick, K; Miyakoshi, T; Miyanaga, N; Norimatsu, T; Rose, S J; Shozaki, T; Shigemori, K; Sunahara, A; Tampo, M; Tanaka, K A; Toyama, Y; Yamanaka, T; Zepf, M

2001-08-23

Modern high-power lasers can generate extreme states of matter that are relevant to astrophysics, equation-of-state studies and fusion energy research. Laser-driven implosions of spherical polymer shells have, for example, achieved an increase in density of 1,000 times relative to the solid state. These densities are large enough to enable controlled fusion, but to achieve energy gain a small volume of compressed fuel (known as the 'spark') must be heated to temperatures of about 108 K (corresponding to thermal energies in excess of 10 keV). In the conventional approach to controlled fusion, the spark is both produced and heated by accurately timed shock waves, but this process requires both precise implosion symmetry and a very large drive energy. In principle, these requirements can be significantly relaxed by performing the compression and fast heating separately; however, this 'fast ignitor' approach also suffers drawbacks, such as propagation losses and deflection of the ultra-intense laser pulse by the plasma surrounding the compressed fuel. Here we employ a new compression geometry that eliminates these problems; we combine production of compressed matter in a laser-driven implosion with picosecond-fast heating by a laser pulse timed to coincide with the peak compression. Our approach therefore permits efficient compression and heating to be carried out simultaneously, providing a route to efficient fusion energy production.

Effect of Laser Powder Bed Fusion Parameters on the Microstructure and Texture Development in Superelastic Ti-18Zr-14Nb Alloy

NASA Astrophysics Data System (ADS)

Kreitcberg, A.; Brailovski, V.; Sheremetyev, V.; Prokoshkin, S.

2017-12-01

The effect of different laser powder bed fusion (L-PBF) parameters on the phase composition, microstructure, and crystallographic texture of Ti-18Zr-14Nb alloy was studied. Two levels of laser power, scanning speed, and hatching space were used, while the layer thickness was kept constant. The resulting volume energy density was ranged from 20 to 60 J/mm3, and the build rate, from 12 to 36 cm3/h. The manufactured coupons were analyzed by X-ray diffractometry, transmission, and scanning electron microscopy. It was found that the greater influence observed on the microstructure and texture development was caused by the value of laser power, while the lowest, by that of hatching space. Based on the results obtained, the processing optimization strategy aimed at improving the density, superelastic, and fatigue properties of the L-PBF manufactured Ti-18Zr-14Nb alloy was proposed.

LLE Review 118 (January-March 2009)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bittle, W., editor

2009-08-03

This issue has the following articles: (1) Applied Plasma Spectroscopy: Laser-Fusion Experiments; (2) Relativistic Electron-Beam Transport Studies Using High-Resolution, Coherent Transition Radiation Imaging; (3) Pressure-Driven, Resistive Magnetohydrodynamic Interchange Instabilities in Laser-Produced, High-Energy-Density Plasmas; (4) Extended Model for Polymer Cholesteric Liquid Crystal Flake Reorientation and Relaxation; (5) Modeling the Effects of Microencapsulation on the Electro-Optic Behavior of Polymer Cholesteric Liquid Crystal Flakes; (6) Capillarity and Dielectrophoresis of Liquid Deuterium; and (7) A Stable Mid-IR, GaSb-Based Diode Laser Source for Cryogenic Target Layering at the OMEGA Laser Facility.

Laser-direct-drive program: Promise, challenge, and path forward

DOE Office of Scientific and Technical Information (OSTI.GOV)

Campbell, E. M.; Goncharov, V. N.; Sangster, T. C.

Along with laser-indirect (x-ray)-drive and magnetic-drive target concepts, laser direct drive is a viable approach to achieving ignition and gain with inertial confinement fusion. In the United States, a national program has been established to demonstrate and understand the physics of laser direct drive. The program utilizes the Omega Laser Facility to conduct implosion and coupling physics at the nominally 30-kJ scale and laser–plasma interaction and coupling physics at the MJ scale at the National Ignition Facility. This paper will discuss the motivation and challenges for laser direct drive and the broad-based program presently underway in the United States.

Laser-direct-drive program: Promise, challenge, and path forward

DOE PAGES

Campbell, E. M.; Goncharov, V. N.; Sangster, T. C.; ...

2017-03-19

Along with laser-indirect (x-ray)-drive and magnetic-drive target concepts, laser direct drive is a viable approach to achieving ignition and gain with inertial confinement fusion. In the United States, a national program has been established to demonstrate and understand the physics of laser direct drive. The program utilizes the Omega Laser Facility to conduct implosion and coupling physics at the nominally 30-kJ scale and laser–plasma interaction and coupling physics at the MJ scale at the National Ignition Facility. This paper will discuss the motivation and challenges for laser direct drive and the broad-based program presently underway in the United States.

Lasers.

ERIC Educational Resources Information Center

Schewe, Phillip F.

1981-01-01

Examines the nature of laser light. Topics include: (1) production and characteristics of laser light; (2) nine types of lasers; (3) five laser techniques including holography; (4) laser spectroscopy; and (5) laser fusion and other applications. (SK)

OPTOELECTRONICS, FIBER OPTICS, AND OTHER ASPECTS OF QUANTUM ELECTRONICS: Delivery of cryotargets to a laser focus

NASA Astrophysics Data System (ADS)

Baranov, G. D.; Koresheva, E. R.; Listratov, V. I.; Merkul'ev, Yu A.; Mineev, G. V.; Nikitenko, A. I.; Osipov, I. E.; Rogachev, A. V.; Tolokonnikov, S. M.; Chumanov, A. N.

1989-08-01

It is suggested that cryogenic targets be delivered to the focus of a laser fusion chamber by a "cryogenic gun" system based on the principle of electromagnetic acceleration of a special ferromagnetic plunger carrying a target. The performance of the acceleration unit of the cryogenic gun is considered. Experimental results are reported.

Focal Laser Ablation of Prostate Cancer: Feasibility of Magnetic Resonance Imaging-Ultrasound Fusion for Guidance.

PubMed

Natarajan, Shyam; Jones, Tonye A; Priester, Alan M; Geoghegan, Rory; Lieu, Patricia; Delfin, Merdie; Felker, Ely; Margolis, Daniel J A; Sisk, Anthony; Pantuck, Allan; Grundfest, Warren; Marks, Leonard S

2017-10-01

Focal laser ablation is a potential treatment in some men with prostate cancer. Currently focal laser ablation is performed by radiologists in a magnetic resonance imaging unit (in bore). We evaluated the safety and feasibility of performing focal laser ablation in a urology clinic (out of bore) using magnetic resonance imaging-ultrasound fusion for guidance. A total of 11 men with intermediate risk prostate cancer were enrolled in this prospective, institutional review board approved pilot study. Magnetic resonance imaging-ultrasound fusion was used to guide laser fibers transrectally into regions of interest harboring intermediate risk prostate cancer. Thermal probes were inserted for real-time monitoring of intraprostatic temperatures during laser activation. Multiparametric magnetic resonance imaging (3 Tesla) was done immediately after treatment and at 6 months along with comprehensive fusion biopsy. Ten of 11 patients were successfully treated while under local anesthesia. Mean procedure time was 95 minutes (range 71 to 105). Posttreatment magnetic resonance imaging revealed a confined zone of nonperfusion in all 10 men. Mean zone volume was 4.3 cc (range 2.1 to 6.0). No CTCAE grade 3 or greater adverse events developed and no changes were observed in urinary or sexual function. At 6 months magnetic resonance imaging-ultrasound fusion biopsy of the treatment site showed no cancer in 3 patients, microfocal Gleason 3 + 3 in another 3 and persistent intermediate risk prostate cancer in 4. Focal laser ablation of prostate cancer appears safe and feasible with the patient under local anesthesia in a urology clinic using magnetic resonance imaging-ultrasound fusion for guidance and thermal probes for monitoring. Further development is necessary to refine out of bore focal laser ablation and additional studies are needed to determine appropriate treatment margins and oncologic efficacy. Copyright © 2017 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

Optimal Path to a Laser Fusion Energy Power Plant

NASA Astrophysics Data System (ADS)

Bodner, Stephen

2013-10-01

There was a decision in the mid 1990s to attempt ignition using indirect-drive targets. It is now obvious that this decision was unjustified. The target design was too geometrically complex, too inefficient, and too far above plasma instability thresholds. By that same time, the mid 1990s, there had also been major advances in the direct-drive target concept. It also was not yet ready for a major test. Now, finally, because of significant advances in target designs, laser-target experiments, and laser development, the direct-drive fusion concept is ready for significant enhancements in funding, on the path to commercial fusion energy. There are two laser contenders. A KrF laser is attractive because of its shortest wavelength, broad bandwidth, and superb beam uniformity. A frequency-converted DPSSL has the disadvantage of inherently narrow bandwidth and longer wavelength, but by combining many beams in parallel one might be able to produce at the target the equivalent of an ultra-broad bandwidth. One or both of these lasers may also meet all of the engineering and economic requirements for a reactor. It is time to further develop and evaluate these two lasers as rep-rate systems, in preparation for a future high-gain fusion test.

Suppression of the chain nuclear fusion reaction based on the p+{sup 11}B reaction because of the deceleration of alpha particles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shmatov, M. L., E-mail: M.Shmatov@mail.ioffe.ru

2016-09-15

It is shown that a rapid deceleration of alpha particles in matter of electron temperature up to 100 keV leads a strong suppression of the chain nuclear fusion reaction on the basis of the p+{sup 11}B reaction with the reproduction of fast protons in the α+{sup 11}B and n+{sup 10}B reactions. The statement that the chain nuclear fusion reaction based on the p+{sup 11}B reaction with an acceleration of {sup 11}B nuclei because of elastic alpha-particle scattering manifests itself in experiments at the PALS (Prague Asterix Laser System) facility is analyzed.

Control of a laser inertial confinement fusion-fission power plant

DOEpatents

Moses, Edward I.; Latkowski, Jeffery F.; Kramer, Kevin J.

2015-10-27

A laser inertial-confinement fusion-fission energy power plant is described. The fusion-fission hybrid system uses inertial confinement fusion to produce neutrons from a fusion reaction of deuterium and tritium. The fusion neutrons drive a sub-critical blanket of fissile or fertile fuel. A coolant circulated through the fuel extracts heat from the fuel that is used to generate electricity. The inertial confinement fusion reaction can be implemented using central hot spot or fast ignition fusion, and direct or indirect drive. The fusion neutrons result in ultra-deep burn-up of the fuel in the fission blanket, thus enabling the burning of nuclear waste. Fuels include depleted uranium, natural uranium, enriched uranium, spent nuclear fuel, thorium, and weapons grade plutonium. LIFE engines can meet worldwide electricity needs in a safe and sustainable manner, while drastically shrinking the highly undesirable stockpiles of depleted uranium, spent nuclear fuel and excess weapons materials.

1.3-microm optically-pumped semiconductor disk laser by wafer fusion.

PubMed

Lyytikäinen, Jari; Rautiainen, Jussi; Toikkanen, Lauri; Sirbu, Alexei; Mereuta, Alexandru; Caliman, Andrei; Kapon, Eli; Okhotnikov, Oleg G

2009-05-25

We report a wafer-fused high power optically-pumped semiconductor disk laser operating at 1.3 microm. An InP-based active medium was fused with a GaAs/AlGaAs distributed Bragg reflector, resulting in an integrated monolithic gain mirror. Over 2.7 W of output power, obtained at temperature of 15 degrees C, represents the best achievement reported to date for this type of lasers. The results reveal an essential advantage of the wafer fusing technique over both monolithically grown AlGaInAs/GaInAsP- and GaInNAs-based structures.

Laser Boron Fusion Reactor With Picosecond Petawatt Block Ignition

NASA Astrophysics Data System (ADS)

Hora, Heinrich; Eliezer, Shalom; Wang, Jiaxiang; Korn, Georg; Nissim, Noaz; Xu, Yan-Xia; Lalousis, Paraskevas; Kirchhoff, Gotz J.; Miley, George H.

2018-05-01

For developing a laser boron fusion reactor driven by picosecond laser pulses of more than 30 petawatts power, advances are reported about computations for the plasma block generation by the dielectric explosion of the interaction. Further results are about the direct drive ignition mechanism by a single laser pulse without the problems of spherical irradiation. For the sufficiently large stopping lengths of the generated alpha particles in the plasma results from other projects can be used.

Femtosecond laser surgery of two-cell mouse embryos: effect on viability, development, and tetraploidization.

PubMed

Osychenko, Alina A; Zalessky, Alexandr D; Kostrov, Andrey N; Ryabova, Anastasia V; Krivokharchenko, Alexander S; Nadtochenko, Viktor A

2017-12-01

The effect of the laser pulse energy and total expose of the energy incident on the embryo blastomere fusion probability was investigated. The probability of the four different events after laser pulse was determined: the fusion of two blastomeres with the following formation of tetraploid embryo, the destruction of the first blastomere occurs, the second blastomere conservation remains intact, the destruction and the death of both cells; two blastomeres were not fused, and no morphological changes occurred. We report on viability and quality of the embryo after laser surgery as a function of the laser energy incident. To characterize embryo quality, the probability of the blastocyst stage achievement was estimated and the blastocyst cells number was calculated. Blastocoel formation is the only event of morphogenesis in the preimplantation development of mammals, so we assumed it as an indicator of the time of embryonic "clocks" and observed it among fused and control embryos. The blastocoel formation time is the same for fused and control embryos. It indicates that embryo clocks were not affected due to blastomere fusion. Thus, the analysis of the fluorescence microscopic images of nuclei in the fused embryo revealed that nuclei fusion does not occur after blastomere fusion. (2017) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

Conceptual design of fast-ignition laser fusion reactor FALCON-D

NASA Astrophysics Data System (ADS)

Goto, T.; Someya, Y.; Ogawa, Y.; Hiwatari, R.; Asaoka, Y.; Okano, K.; Sunahara, A.; Johzaki, T.

2009-07-01

A new conceptual design of the laser fusion power plant FALCON-D (Fast-ignition Advanced Laser fusion reactor CONcept with a Dry wall chamber) has been proposed. The fast-ignition method can achieve sufficient fusion gain for a commercial operation (~100) with about 10 times smaller fusion yield than the conventional central ignition method. FALCON-D makes full use of this property and aims at designing with a compact dry wall chamber (5-6 m radius). 1D/2D simulations by hydrodynamic codes showed a possibility of achieving sufficient gain with a laser energy of 400 kJ, i.e. a 40 MJ target yield. The design feasibility of the compact dry wall chamber and the solid breeder blanket system was shown through thermomechanical analysis of the dry wall and neutronics analysis of the blanket system. Moderate electric output (~400 MWe) can be achieved with a high repetition (30 Hz) laser. This dry wall reactor concept not only reduces several difficulties associated with a liquid wall system but also enables a simple cask maintenance method for the replacement of the blanket system, which can shorten the maintenance period. The basic idea of the maintenance method for the final optics system has also been proposed. Some critical R&D issues required for this design are also discussed.

Microstructure formation and fracturing characteristics of grey cast iron repaired using laser.

PubMed

Yi, Peng; Xu, Pengyun; Fan, Changfeng; Yang, Guanghui; Liu, Dan; Shi, Yongjun

2014-01-01

The repairing technology based on laser rapid fusion is becoming an important tool for fixing grey cast iron equipment efficiently. A laser repairing protocol was developed using Fe-based alloy powders as material. The microstructure and fracturing feature of the repaired zone (RZ) were analyzed. The results showed that regionally organized RZ with good density and reliable metallurgical bond can be achieved by laser repairing. At the bottom of RZ, dendrites existed in similar direction and extended to the secondary RZ, making the grains grow extensively with inheritance with isometric grains closer to the surface substrate. The strength of the grey cast iron base material was maintained by laser repairing. The base material and RZ were combined with robust strength and fracture resistance. The prevention and deflection of cracking process were analyzed using a cracking process model and showed that the overall crack toughness of the materials increased.

Microstructure Formation and Fracturing Characteristics of Grey Cast Iron Repaired Using Laser

PubMed Central

Liu, Dan; Shi, Yongjun

2014-01-01

The repairing technology based on laser rapid fusion is becoming an important tool for fixing grey cast iron equipment efficiently. A laser repairing protocol was developed using Fe-based alloy powders as material. The microstructure and fracturing feature of the repaired zone (RZ) were analyzed. The results showed that regionally organized RZ with good density and reliable metallurgical bond can be achieved by laser repairing. At the bottom of RZ, dendrites existed in similar direction and extended to the secondary RZ, making the grains grow extensively with inheritance with isometric grains closer to the surface substrate. The strength of the grey cast iron base material was maintained by laser repairing. The base material and RZ were combined with robust strength and fracture resistance. The prevention and deflection of cracking process were analyzed using a cracking process model and showed that the overall crack toughness of the materials increased. PMID:25032230

Pulsed Laser Beam Welding of Pd43Cu27Ni10P20 Bulk Metallic Glass.

PubMed

Shao, Ling; Datye, Amit; Huang, Jiankang; Ketkaew, Jittisa; Woo Sohn, Sung; Zhao, Shaofan; Wu, Sujun; Zhang, Yuming; Schwarz, Udo D; Schroers, Jan

2017-08-11

We used pulsed laser beam welding method to join Pd 43 Cu 27 Ni 10 P 20 (at.%) bulk metallic glass and characterized the properties of the joint. Fusion zone and heat-affected zone in the weld joint can be maintained completely amorphous as confirmed by X-ray diffraction and differential scanning calorimetry. No visible defects were observed in the weld joint. Nanoindentation and bend tests were carried out to determine the mechanical properties of the weld joint. Fusion zone and heat-affected zone exhibit very similar elastic moduli and hardness when compared to the base material, and the weld joint shows high ductility in bending which is accomplished through the operation of multiple shear bands. Our results reveal that pulsed laser beam welding under appropriate processing parameters provides a practical viable method to join bulk metallic glasses.

Dissimilar material joining using laser (aluminum to steel using zinc-based filler wire)

NASA Astrophysics Data System (ADS)

Mathieu, Alexandre; Shabadi, Rajashekar; Deschamps, Alexis; Suery, Michel; Matteï, Simone; Grevey, Dominique; Cicala, Eugen

2007-04-01

Joining steel with aluminum involving the fusion of one or both materials is possible by laser beam welding technique. This paper describes a method, called laser braze welding, which is a suitable process to realize this structure. The main problem with thermal joining of steel/aluminum assembly with processes such as TIG or MIG is the formation of fragile intermetallic phases, which are detrimental to the mechanical performances of such joints. Braze welding permits a localized fusion of the materials resulting in a limitation on the growth of fragile phases. This article presents the results of a statistical approach for an overlap assembly configuration using a filler wire composed of 85% Zn and 15% Al. Tensile tests carried on these assemblies demonstrate a good performance of the joints. The fracture mechanisms of the joints are analyzed by a detailed characterization of the seams.

Simulations of High-Gain Shock-Ignited Inertial-Confinement-Fusion Implosions Using Less Than 1 MJ of Direct KrF Laser Energy

DTIC Science & Technology

2009-05-01

transport, and thermonuclear burn. Using FAST, three classes of shock-ignited targets were designed that achieve one-dimensional fusion - energy gains in the...MJ) G a in Figure 1: Results of one-dimensional simulations showing the fusion energy gain as a function of KrF laser energy for three classes of...rises smoothly (according to a double power (a) Spike width: 160 ps (b) Spike power: 1530 TW Figure 4: Examples of fusion - energy gain contours for a shock

Fusion of laser and image sensory data for 3-D modeling of the free navigation space

NASA Technical Reports Server (NTRS)

Mass, M.; Moghaddamzadeh, A.; Bourbakis, N.

1994-01-01

A fusion technique which combines two different types of sensory data for 3-D modeling of a navigation space is presented. The sensory data is generated by a vision camera and a laser scanner. The problem of different resolutions for these sensory data was solved by reduced image resolution, fusion of different data, and use of a fuzzy image segmentation technique.

Comparison of the Recently proposed Super Marx Generator Approach to Thermonuclear Ignition with the DT Laser Fusion-Fission Hybrid Concept (LIFE) by the Lawrence Livermore National Laboratory.

NASA Astrophysics Data System (ADS)

Winterberg, Friedwardt

2009-05-01

The recently proposed Super Marx pure deuterium micro-detonation ignition concept [1] is compared to the Lawrence Livermore National Ignition Facility (NIF) laser DT fusion-fission hybrid concept (LIFE) [2]. A typical example of the LIFE concept is a fusion gain 30, and a fission gain of 10, making up for a total gain of 300, with about 10 times more energy released into fission as compared to fusion. This means a substantial release of fission products, as in fusion-less pure fission reactors. In the Super Marx approach for the ignition of a pure deuterium micro-detonation gains of the same magnitude can in theory be reached. If the theoretical prediction can be supported by more elaborate calculations, the Super Marx approach is likely to make lasers obsolete as a means for the ignition of thermonuclear micro-explosions. [1] ``Ignition of a Deuterium Micro-Detonation with a Gigavolt Super Marx Generator,'' Winterberg, F., Journal of Fusion Energy, Springer, 2008. http://www.springerlink.com/content/r2j046177j331241/fulltext.pdf. [2] ``LIFE: Clean Energy from Nuclear Waste,'' https://lasers.llnl.gov/missions/energy&_slash;for&_slash;the&_slash;future/life/

Next generation laser for Inertial Confinement Fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marshall, C.D.; Beach, J.; Bibeau, C.

1997-07-18

We are in the process of developing and building the ``Mercury`` laser system as the first in a series of a new generation of diode-pumped solid-state Inertial Confinement Fusion (ICF) lasers at LLNL. Mercury will be the first integrated demonstration of a scalable laser architecture compatible with advanced high energy density (HED) physics applications. Primary performance goals include 10% efficiencies at 10 Hz and a 1-10 ns pulse with 1{omega} energies of 100 J and with 2{omega}/3{omega} frequency conversion.

A Laser Based Fusion Test Facility

DTIC Science & Technology

2008-10-01

Nike laser have explored the intensities employed by these Report Documentation Page Form ApprovedOMB No. 0704-0188 Public reporting burden for the...and best beam smoothing with KrF makes it the most resistant to such instability. As discussed above, recent experiments using the Nike facility...support this expectation. There is ongoing experimental and theoretical work on Nike , Omega, and eventually NIF to determine these intensity limits

Numerical models of laser fusion of intestinal tissues.

PubMed

Pearce, John A

2009-01-01

Numerical models of continuous wave Tm:YAG thermal fusion in rat intestinal tissues were compared to experiment. Optical and thermal FDM models that included tissue damage based on Arrhenius kinetics were used to predict birefringence loss in collagen as the standard of comparison. The models also predicted collagen shrinkage, jellification and water loss. The inclusion of variable optical and thermal properties is essential to achieve favorable agreement between predicted and measured damage boundaries.

Full-wave and ray-based modeling of cross-beam energy transfer between laser beams with distributed phase plates and polarization smoothing

DOE PAGES

Follett, R. K.; Edgell, D. H.; Froula, D. H.; ...

2017-10-20

Radiation-hydrodynamic simulations of inertial confinement fusion (ICF) experiments rely on ray-based cross-beam energy transfer (CBET) models to calculate laser energy deposition. The ray-based models assume locally plane-wave laser beams and polarization averaged incoherence between laser speckles for beams with polarization smoothing. The impact of beam speckle and polarization smoothing on crossbeam energy transfer (CBET) are studied using the 3-D wave-based laser-plasma-interaction code LPSE. The results indicate that ray-based models under predict CBET when the assumption of spatially averaged longitudinal incoherence across the CBET interaction region is violated. A model for CBET between linearly-polarized speckled beams is presented that uses raymore » tracing to solve for the real speckle pattern of the unperturbed laser beams within the eikonal approximation and gives excellent agreement with the wavebased calculations. Lastly, OMEGA-scale 2-D LPSE calculations using ICF relevant plasma conditions suggest that the impact of beam speckle on laser absorption calculations in ICF implosions is small (< 1%).« less

Full-wave and ray-based modeling of cross-beam energy transfer between laser beams with distributed phase plates and polarization smoothing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Follett, R. K.; Edgell, D. H.; Froula, D. H.

Radiation-hydrodynamic simulations of inertial confinement fusion (ICF) experiments rely on ray-based cross-beam energy transfer (CBET) models to calculate laser energy deposition. The ray-based models assume locally plane-wave laser beams and polarization averaged incoherence between laser speckles for beams with polarization smoothing. The impact of beam speckle and polarization smoothing on crossbeam energy transfer (CBET) are studied using the 3-D wave-based laser-plasma-interaction code LPSE. The results indicate that ray-based models under predict CBET when the assumption of spatially averaged longitudinal incoherence across the CBET interaction region is violated. A model for CBET between linearly-polarized speckled beams is presented that uses raymore » tracing to solve for the real speckle pattern of the unperturbed laser beams within the eikonal approximation and gives excellent agreement with the wavebased calculations. Lastly, OMEGA-scale 2-D LPSE calculations using ICF relevant plasma conditions suggest that the impact of beam speckle on laser absorption calculations in ICF implosions is small (< 1%).« less

Electro-optic harmonic conversion to switch a laser beam out of a cavity

DOEpatents

Haas, R.A.; Henesian, M.A.

1984-10-19

The present invention relates to switching laser beams out of laser cavities, and more particularly, it relates to the use of generating harmonics of the laser beam to accomplish the switching. When laser light is generatd in a laser cavity the problem arises of how to switch the laser light out of the cavity in order to make use of the resulting laser beam in a well known multitude of ways. These uses include range finding, communication, remote sensing, medical surgery, laser fusion applications and many more. The switch-out problem becomes more difficult as the size of the laser aperture grows such as in laser fusion applications. The final amplifier stages of the Nova and Novette lasers at Lawrence Livermore National Laboratory are 46 centimeters with the laser beam expanded to 74 centimeters thereafter. Larger aperture lasers are planned.

Laser fusion neutron source employing compression with short pulse lasers

DOEpatents

Sefcik, Joseph A; Wilks, Scott C

2013-11-05

A method and system for achieving fusion is provided. The method includes providing laser source that generates a laser beam and a target that includes a capsule embedded in the target and filled with DT gas. The laser beam is directed at the target. The laser beam helps create an electron beam within the target. The electron beam heats the capsule, the DT gas, and the area surrounding the capsule. At a certain point equilibrium is reached. At the equilibrium point, the capsule implodes and generates enough pressure on the DT gas to ignite the DT gas and fuse the DT gas nuclei.

Liquid level sensor based on fiber ring laser with single-mode-offset coreless-single-mode fiber structure

NASA Astrophysics Data System (ADS)

Wang, Zixiao; Tan, Zhongwei; Xing, Rui; Liang, Linjun; Qi, Yanhui; Jian, Shuisheng

2016-10-01

A novel reflective liquid level sensor based on single-mode-offset coreless-single-mode (SOCS) fiber structure is proposed and experimentally demonstrated. Theory analyses and experimental results indicate that offset fusion can remarkably enhance the sensitivity of sensor. Ending-reflecting structure makes the sensor compact and easy to deploy. Meanwhile, we propose a laser sensing system, and the SOCS structure is used as sensing head and laser filter simultaneously. Experimental results show that laser spectra with high optical signal-to-noise ratio (-30 dB) and narrow 3-dB bandwidth (<0.15 nm) are achieved. Various liquids with different indices are used for liquid level sensing, besides, the refractive index sensitivity is also investigated. In measurement range, the sensing system presents steady laser output.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osychenko, A A; Zalesskii, A D; Krivokharchenko, A S

Using the method of femtosecond laser surgery we study the fusion of two-cell mouse embryos under the action of tightly focused femtosecond laser radiation with the fusion efficiency reaching 60%. The detailed statistical analysis of the efficiency of blastomere fusion and development of the embryo up to the blastocyst stage after exposure of the embryos from different mice to a femtosecond pulse is presented. It is shown that the efficiency of blastocyst formation essentially depends on the biological characteristics of the embryo, namely, the strain and age of the donor mouse. The possibility of obtaining hexaploid embryonal cells using themore » methods of femtosecond laser surgery is demonstrated. (extreme light fields and their applications)« less

Study of self-focusing of Non Gaussian laser beam in a plasma with density variation using moment theory approach

NASA Astrophysics Data System (ADS)

Pathak, Nidhi; Kaur, Sukhdeep; Singh, Sukhmander

2018-05-01

In this paper, self-focusing/defocusing effects have been studied by taking into account the combined effect of ponder-motive and relativistic non linearity during the laser plasma interaction with density variation. The formulation is based on the numerical analysis of second order nonlinear differential equation for appropriate set of laser and plasma parameters by employing moment theory approach. We found that self-focusing increases with increasing the laser intensity and density variation. The results obtained are valuable in high harmonic generation, inertial confinement fusion and charge particle acceleration.

Fusion energy with lasers, direct drive targets, and dry wall chambers

NASA Astrophysics Data System (ADS)

Sethian, J. D.; Friedman, M.; Lehmberg, R. H.; Myers, M.; Obenschain, S. P.; Giuliani, J.; Kepple, P.; Schmitt, A. J.; Colombant, D.; Gardner, J.; Hegeler, F.; Wolford, M.; Swanekamp, S. B.; Weidenheimer, D.; Welch, D.; Rose, D.; Payne, S.; Bibeau, C.; Baraymian, A.; Beach, R.; Schaffers, K.; Freitas, B.; Skulina, K.; Meier, W.; Latkowski, J.; Perkins, L. J.; Goodin, D.; Petzoldt, R.; Stephens, E.; Najmabadi, F.; Tillack, M.; Raffray, R.; Dragojlovic, Z.; Haynes, D.; Peterson, R.; Kulcinski, G.; Hoffer, J.; Geller, D.; Schroen, D.; Streit, J.; Olson, C.; Tanaka, T.; Renk, T.; Rochau, G.; Snead, L.; Ghoneim, N.; Lucas, G.

2003-12-01

A coordinated, focused effort is underway to develop Laser Inertial Fusion Energy. The key components are developed in concert with one another and the science and engineering issues are addressed concurrently. Recent advances include: target designs have been evaluated that show it could be possible to achieve the high gains (>100) needed for a practical fusion system.These designs feature a low-density CH foam that is wicked with solid DT and over-coated with a thin high-Z layer. These results have been verified with three independent one-dimensional codes, and are now being evaluated with two- and three-dimensional codes. Two types of lasers are under development: Krypton Fluoride (KrF) gas lasers and Diode Pumped Solid State Lasers (DPSSL). Both have recently achieved repetitive 'first light', and both have made progress in meeting the fusion energy requirements for durability, efficiency, and cost. This paper also presents the advances in development of chamber operating windows (target survival plus no wall erosion), final optics (aluminium at grazing incidence has high reflectivity and exceeds the required laser damage threshold), target fabrication (demonstration of smooth DT ice layers grown over foams, batch production of foam shells, and appropriate high-Z overcoats), and target injection (new facility for target injection and tracking studies).

Wavefront control of high-power laser beams in the National Ignition Facility (NIF)

NASA Astrophysics Data System (ADS)

Zacharias, Richard A.; Bliss, Erlan S.; Winters, Scott; Sacks, Richard A.; Feldman, Mark; Grey, Andrew; Koch, Jeffrey A.; Stolz, Christopher J.; Toeppen, John S.; Van Atta, Lewis; Woods, Bruce W.

2000-04-01

The use of lasers as the driver for inertial confinement fusion and weapons physics experiments is based on their ability to produce high-energy short pulses in a beam with low divergence. Indeed, the focusability of high quality laser beams far exceeds alternate technologies and is a major factor in the rationale for building high power lasers for such applications. The National Ignition Facility (NIF) is a large, 192-beam, high-power laser facility under construction at the Lawrence Livermore National Laboratory for fusion and weapons physics experiments. Its uncorrected minimum focal spot size is limited by laser system aberrations. The NIF includes a Wavefront Control System to correct these aberrations to yield a focal spot small enough for its applications. Sources of aberrations to be corrected include prompt pump-induced distortions in the laser amplifiers, previous-shot thermal distortions, beam off-axis effects, and gravity, mounting, and coating-induced optic distortions. Aberrations from gas density variations and optic-manufacturing figure errors are also partially corrected. This paper provides an overview of the NIF Wavefront Control System and describes the target spot size performance improvement it affords. It describes provisions made to accommodate the NIF's high fluence (laser beam and flashlamp), large wavefront correction range, wavefront temporal bandwidth, temperature and humidity variations, cleanliness requirements, and exception handling requirements (e.g. wavefront out-of-limits conditions).

Nuclear Fusion In Gases Of Deuterium Clusters And Hot Electron Generation In Droplet Sprays Under Irradiation With An Intense Femtosecond Laser

DOE Office of Scientific and Technical Information (OSTI.GOV)

T. Ditmire; Zweiback, J; Cowan, T E

In conclusion, we have observed the production of 2.45 MeV deuterium fusion neutrons when a gas of deuterium clusters is irradiated with a 120 mJ, 35 fs laser pulse. When the focal position is optimized, we have observed as many as 10{sup 4} neutrons per laser shot. This yield is consistent with some simple estimates for the fusion yield. We also find that the fusion yield is a sensitive function of the deuterium cluster size in the target jet, a consequence of the Coulomb explosion origin of the fast deuterons. We also find that the neutron pulse duration is fast,more » with a characteristic burn time of well under 1 ns. This experiment may represent a means for producing a compact, table-top source of short pulse fusion neutrons for applications. Furthermore, we have measured hard x-ray yield from femtosecond laser interactions with both solid and micron scale droplet targets. Strong hard x-ray production is observed from both targets. However, the inferred electron temperature is somewhat higher in the case of irradiation of the droplets. These data are consistent with PIC simulations. This finding indicates that quite unique hot electron dynamics occur during the irradiation of wavelength scale particles by an intense laser field and likely warrants further study.« less

Inertial Confinement Fusion and the National Ignition Facility (NIF)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ross, P.

2012-08-29

Inertial confinement fusion (ICF) seeks to provide sustainable fusion energy by compressing frozen deuterium and tritium fuel to extremely high densities. The advantages of fusion vs. fission are discussed, including total energy per reaction and energy per nucleon. The Lawson Criterion, defining the requirements for ignition, is derived and explained. Different confinement methods and their implications are discussed. The feasibility of creating a power plant using ICF is analyzed using realistic and feasible numbers. The National Ignition Facility (NIF) at Lawrence Livermore National Laboratory is shown as a significant step forward toward making a fusion power plant based on ICF.more » NIF is the world’s largest laser, delivering 1.8 MJ of energy, with a peak power greater than 500 TW. NIF is actively striving toward the goal of fusion energy. Other uses for NIF are discussed.« less

Inertial-confinement fusion with lasers

DOE PAGES

Betti, R.; Hurricane, O. A.

2016-05-03

The quest for controlled fusion energy has been ongoing for over a half century. The demonstration of ignition and energy gain from thermonuclear fuels in the laboratory has been a major goal of fusion research for decades. Thermonuclear ignition is widely considered a milestone in the development of fusion energy, as well as a major scientific achievement with important applications to national security and basic sciences. The U.S. is arguably the world leader in the inertial con fment approach to fusion and has invested in large facilities to pursue it with the objective of establishing the science related to themore » safety and reliability of the stockpile of nuclear weapons. Even though significant progress has been made in recent years, major challenges still remain in the quest for thermonuclear ignition via laser fusion.« less

Microstructure Characterization of Fiber Laser Welds of S690QL High-Strength Steels

NASA Astrophysics Data System (ADS)

Li, Baoming; Xu, Peiquan; Lu, Fenggui; Gong, Hongying; Cui, Haichao; Liu, Chuangen

2018-02-01

The use of fiber laser welding to join S690QL steels has attracted interest in the field of construction and assembly. Herein, 13-mm-thick S690QL welded joints were obtained without filler materials using the fiber laser. The as-welded microstructures and the impact energies of the joints were characterized and measured using electron microscopy in conjunction with high-resolution transmission electron images, X-ray diffraction, and impact tests. The results indicated that a single-sided welding technique could be used to join S690QL steels up to a thickness of 12 mm (fail to fuse the joint in the root) when the laser power is equal to 12 kW (scan speed 1 m/min). Double-side welding technique allows better weld penetration and better control of heat distribution. Observation of the samples showed that the fusion zone exhibited bainitic and martensitic microstructures with increased amounts of martensites (Ms) compared with the base materials. Also, the grains in the fusion zone increased in coarseness as the heat input was increased. The fusion zone exhibited increased hardness (397 HV0.2) while exhibiting a simultaneous decrease in the impact toughness. The maximum impact energy value of 26 J was obtained from the single-side-welded sample, which is greater than those obtained from the double-side-welded samples (maximum of 18 J). Many more dislocations and plastic deformations were found in the fusion zone than the heat-affected zone in the joint, which hardened the joints and lowered the impact toughness. The microstructures characterized by FTEM-energy-dispersive X-ray spectrometer also exhibited laths of M, as well as stacking faults and dislocations featuring high-density, interfacial structure ledges that occur between the high-angle grain boundaries and the M and bainite.

Scaling mechanisms of vapour/plasma shielding from laser-produced plasmas to magnetic fusion regimes

NASA Astrophysics Data System (ADS)

Sizyuk, Tatyana; Hassanein, Ahmed

2014-02-01

The plasma shielding effect is a well-known mechanism in laser-produced plasmas (LPPs) reducing laser photon transmission to the target and, as a result, significantly reducing target heating and erosion. The shielding effect is less pronounced at low laser intensities, when low evaporation rate together with vapour/plasma expansion processes prevent establishment of a dense plasma layer above the surface. Plasma shielding also loses its effectiveness at high laser intensities when the formed hot dense plasma plume causes extensive target erosion due to radiation fluxes back to the surface. The magnitude of emitted radiation fluxes from such a plasma is similar to or slightly higher than the laser photon flux in the low shielding regime. Thus, shielding efficiency in LPPs has a peak that depends on the laser beam parameters and the target material. A similar tendency is also expected in other plasma-operating devices such as tokamaks of magnetic fusion energy (MFE) reactors during transient plasma operation and disruptions on chamber walls when deposition of the high-energy transient plasma can cause severe erosion and damage to the plasma-facing and nearby components. A detailed analysis of these abnormal events and their consequences in future power reactors is limited in current tokamak reactors. Predictions for high-power future tokamaks are possible only through comprehensive, time-consuming and rigorous modelling. We developed scaling mechanisms, based on modelling of LPP devices with their typical temporal and spatial scales, to simulate tokamak abnormal operating regimes to study wall erosion, plasma shielding and radiation under MFE reactor conditions. We found an analogy in regimes and results of carbon and tungsten erosion of the divertor surface in ITER-like reactors with erosion due to laser irradiation. Such an approach will allow utilizing validated modelling combined with well-designed and well-diagnosed LPP experimental studies for predicting consequences of plasma instabilities in complex fusion environment, which are of serious concern for successful energy production.

Theoretical and experimental aspects of laser cutting with a direct diode laser

NASA Astrophysics Data System (ADS)

Costa Rodrigues, G.; Pencinovsky, J.; Cuypers, M.; Duflou, J. R.

2014-10-01

Recent developments in beam coupling techniques have made it possible to scale up the power of diode lasers with a laser beam quality suitable for laser cutting of metal sheets. In this paper a prototype of a Direct Diode Laser (DDL) source (BPP of 22 mm-mrad) is analyzed in terms of efficiency and cut performance and compared with two established technologies, CO2 and fiber lasers. An analytical model based on absorption calculations is used to predict the performance of the studied laser source with a good agreement with experimental results. Furthermore results of fusion cutting of stainless steel and aluminium alloys as well as oxygen cutting of structural steel are presented, demonstrating that industrial relevant cutting speeds with high cutting quality can now be achieved with DDL.

Next-generation laser for Inertial Confinement Fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marshall, C.D.; Deach, R.J.; Bibeau, C.

1997-09-29

We report on the progress in developing and building the Mercury laser system as the first in a series of a new generation of diode- pumped solid-state Inertial Confinement Fusion (ICF) lasers at Lawrence Livermore National Laboratory (LLNL). Mercury will be the first integrated demonstration of a scalable laser architecture compatible with advanced high energy density (HED) physics applications. Primary performance goals include 10% efficiencies at 10 Hz and a 1-10 ns pulse with 1 omega energies of 100 J and with 2 omega/3 omega frequency conversion.

Demonstration of Ignition Radiation Temperatures in Indirect-Drive Inertial Confinement Fusion Hohlraums

NASA Astrophysics Data System (ADS)

Glenzer, S. H.; MacGowan, B. J.; Meezan, N. B.; Adams, P. A.; Alfonso, J. B.; Alger, E. T.; Alherz, Z.; Alvarez, L. F.; Alvarez, S. S.; Amick, P. V.; Andersson, K. S.; Andrews, S. D.; Antonini, G. J.; Arnold, P. A.; Atkinson, D. P.; Auyang, L.; Azevedo, S. G.; Balaoing, B. N. M.; Baltz, J. A.; Barbosa, F.; Bardsley, G. W.; Barker, D. A.; Barnes, A. I.; Baron, A.; Beeler, R. G.; Beeman, B. V.; Belk, L. R.; Bell, J. C.; Bell, P. M.; Berger, R. L.; Bergonia, M. A.; Bernardez, L. J.; Berzins, L. V.; Bettenhausen, R. C.; Bezerides, L.; Bhandarkar, S. D.; Bishop, C. L.; Bond, E. J.; Bopp, D. R.; Borgman, J. A.; Bower, J. R.; Bowers, G. A.; Bowers, M. W.; Boyle, D. T.; Bradley, D. K.; Bragg, J. L.; Braucht, J.; Brinkerhoff, D. L.; Browning, D. F.; Brunton, G. K.; Burkhart, S. C.; Burns, S. R.; Burns, K. E.; Burr, B.; Burrows, L. M.; Butlin, R. K.; Cahayag, N. J.; Callahan, D. A.; Cardinale, P. S.; Carey, R. W.; Carlson, J. W.; Casey, A. D.; Castro, C.; Celeste, J. R.; Chakicherla, A. Y.; Chambers, F. W.; Chan, C.; Chandrasekaran, H.; Chang, C.; Chapman, R. F.; Charron, K.; Chen, Y.; Christensen, M. J.; Churby, A. J.; Clancy, T. J.; Cline, B. D.; Clowdus, L. C.; Cocherell, D. G.; Coffield, F. E.; Cohen, S. J.; Costa, R. L.; Cox, J. R.; Curnow, G. M.; Dailey, M. J.; Danforth, P. M.; Darbee, R.; Datte, P. S.; Davis, J. A.; Deis, G. A.; Demaret, R. D.; Dewald, E. L.; di Nicola, P.; di Nicola, J. M.; Divol, L.; Dixit, S.; Dobson, D. B.; Doppner, T.; Driscoll, J. D.; Dugorepec, J.; Duncan, J. J.; Dupuy, P. C.; Dzenitis, E. G.; Eckart, M. J.; Edson, S. L.; Edwards, G. J.; Edwards, M. J.; Edwards, O. D.; Edwards, P. W.; Ellefson, J. C.; Ellerbee, C. H.; Erbert, G. V.; Estes, C. M.; Fabyan, W. J.; Fallejo, R. N.; Fedorov, M.; Felker, B.; Fink, J. T.; Finney, M. D.; Finnie, L. F.; Fischer, M. J.; Fisher, J. M.; Fishler, B. T.; Florio, J. W.; Forsman, A.; Foxworthy, C. B.; Franks, R. M.; Frazier, T.; Frieder, G.; Fung, T.; Gawinski, G. N.; Gibson, C. R.; Giraldez, E.; Glenn, S. M.; Golick, B. P.; Gonzales, H.; Gonzales, S. A.; Gonzalez, M. J.; Griffin, K. L.; Grippen, J.; Gross, S. M.; Gschweng, P. H.; Gururangan, G.; Gu, K.; Haan, S. W.; Hahn, S. R.; Haid, B. J.; Hamblen, J. E.; Hammel, B. A.; Hamza, A. V.; Hardy, D. L.; Hart, D. R.; Hartley, R. G.; Haynam, C. A.; Heestand, G. M.; Hermann, M. R.; Hermes, G. L.; Hey, D. S.; Hibbard, R. L.; Hicks, D. G.; Hinkel, D. E.; Hipple, D. L.; Hitchcock, J. D.; Hodtwalker, D. L.; Holder, J. P.; Hollis, J. D.; Holtmeier, G. M.; Huber, S. R.; Huey, A. W.; Hulsey, D. N.; Hunter, S. L.; Huppler, T. R.; Hutton, M. S.; Izumi, N.; Jackson, J. L.; Jackson, M. A.; Jancaitis, K. S.; Jedlovec, D. R.; Johnson, B.; Johnson, M. C.; Johnson, T.; Johnston, M. P.; Jones, O. S.; Kalantar, D. H.; Kamperschroer, J. H.; Kauffman, R. L.; Keating, G. A.; Kegelmeyer, L. M.; Kenitzer, S. L.; Kimbrough, J. R.; King, K.; Kirkwood, R. K.; Klingmann, J. L.; Knittel, K. M.; Kohut, T. R.; Koka, K. G.; Kramer, S. W.; Krammen, J. E.; Krauter, K. G.; Krauter, G. W.; Krieger, E. K.; Kroll, J. J.; La Fortune, K. N.; Lagin, L. J.; Lakamsani, V. K.; Landen, O. L.; Lane, S. W.; Langdon, A. B.; Langer, S. H.; Lao, N.; Larson, D. W.; Latray, D.; Lau, G. T.; Le Pape, S.; Lechleiter, B. L.; Lee, Y.; Lee, T. L.; Li, J.; Liebman, J. A.; Lindl, J. D.; Locke, S. F.; Loey, H. K.; London, R. A.; Lopez, F. J.; Lord, D. M.; Lowe-Webb, R. R.; Lown, J. G.; Ludwigsen, A. P.; Lum, N. W.; Lyons, R. R.; Ma, T.; MacKinnon, A. J.; Magat, M. D.; Maloy, D. T.; Malsbury, T. N.; Markham, G.; Marquez, R. M.; Marsh, A. A.; Marshall, C. D.; Marshall, S. R.; Maslennikov, I. L.; Mathisen, D. G.; Mauger, G. J.; Mauvais, M.-Y.; McBride, J. A.; McCarville, T.; McCloud, J. B.; McGrew, A.; McHale, B.; Macphee, A. G.; Meeker, J. F.; Merill, J. S.; Mertens, E. P.; Michel, P. A.; Miller, M. G.; Mills, T.; Milovich, J. L.; Miramontes, R.; Montesanti, R. C.; Montoya, M. M.; Moody, J.; Moody, J. D.; Moreno, K. A.; Morris, J.; Morriston, K. M.; Nelson, J. R.; Neto, M.; Neumann, J. D.; Ng, E.; Ngo, Q. M.; Olejniczak, B. L.; Olson, R. E.; Orsi, N. L.; Owens, M. W.; Padilla, E. H.; Pannell, T. M.; Parham, T. G.; Patterson, R. W., Jr.; Pavel, G.; Prasad, R. R.; Pendlton, D.; Penko, F. A.; Pepmeier, B. L.; Petersen, D. E.; Phillips, T. W.; Pigg, D.; Piston, K. W.; Pletcher, K. D.; Powell, C. L.; Radousky, H. B.; Raimondi, B. S.; Ralph, J. E.; Rampke, R. L.; Reed, R. K.; Reid, W. A.; Rekow, V. V.; Reynolds, J. L.; Rhodes, J. J.; Richardson, M. J.; Rinnert, R. J.; Riordan, B. P.; Rivenes, A. S.; Rivera, A. T.; Roberts, C. J.; Robinson, J. A.; Robinson, R. B.; Robison, S. R.; Rodriguez, O. R.; Rogers, S. P.; Rosen, M. D.; Ross, G. F.; Runkel, M.; Runtal, A. S.; Sacks, R. A.; Sailors, S. F.; Salmon, J. T.; Salmonson, J. D.; Saunders, R. L.; Schaffer, J. R.; Schindler, T. M.; Schmitt, M. J.; Schneider, M. B.; Segraves, K. S.; Shaw, M. J.; Sheldrick, M. E.; Shelton, R. T.; Shiflett, M. K.; Shiromizu, S. J.; Shor, M.; Silva, L. L.; Silva, S. A.; Skulina, K. M.; Smauley, D. A.; Smith, B. E.; Smith, L. K.; Solomon, A. L.; Sommer, S.; Soto, J. G.; Spafford, N. I.; Speck, D. E.; Springer, P. T.; Stadermann, M.; Stanley, F.; Stone, T. G.; Stout, E. A.; Stratton, P. L.; Strausser, R. J.; Suter, L. J.; Sweet, W.; Swisher, M. F.; Tappero, J. D.; Tassano, J. B.; Taylor, J. S.; Tekle, E. A.; Thai, C.; Thomas, C. A.; Thomas, A.; Throop, A. L.; Tietbohl, G. L.; Tillman, J. M.; Town, R. P. J.; Townsend, S. L.; Tribbey, K. L.; Trummer, D.; Truong, J.; Vaher, J.; Valadez, M.; van Arsdall, P.; van Prooyen, A. J.; Vergel de Dios, E. O.; Vergino, M. D.; Vernon, S. P.; Vickers, J. L.; Villanueva, G. T.; Vitalich, M. A.; Vonhof, S. A.; Wade, F. E.; Wallace, R. J.; Warren, C. T.; Warrick, A. L.; Watkins, J.; Weaver, S.; Wegner, P. J.; Weingart, M. A.; Wen, J.; White, K. S.; Whitman, P. K.; Widmann, K.; Widmayer, C. C.; Wilhelmsen, K.; Williams, E. A.; Williams, W. H.; Willis, L.; Wilson, E. F.; Wilson, B. A.; Witte, M. C.; Work, K.; Yang, P. S.; Young, B. K.; Youngblood, K. P.; Zacharias, R. A.; Zaleski, T.; Zapata, P. G.; Zhang, H.; Zielinski, J. S.; Kline, J. L.; Kyrala, G. A.; Niemann, C.; Kilkenny, J. D.; Nikroo, A.; van Wonterghem, B. M.; Atherton, L. J.; Moses, E. I.

2011-02-01

We demonstrate the hohlraum radiation temperature and symmetry required for ignition-scale inertial confinement fusion capsule implosions. Cryogenic gas-filled hohlraums with 2.2 mm-diameter capsules are heated with unprecedented laser energies of 1.2 MJ delivered by 192 ultraviolet laser beams on the National Ignition Facility. Laser backscatter measurements show that these hohlraums absorb 87% to 91% of the incident laser power resulting in peak radiation temperatures of TRAD=300eV and a symmetric implosion to a 100μm diameter hot core.

Electron Shock Ignition of Inertial Fusion Targets

NASA Astrophysics Data System (ADS)

Shang, W. L.; Betti, R.; Hu, S. X.; Woo, K.; Hao, L.; Ren, C.; Christopherson, A. R.; Bose, A.; Theobald, W.

2017-11-01

It is shown that inertial confinement fusion targets designed with low implosion velocities can be shock-ignited using laser-plasma interaction generated hot electrons (hot-e 's) to obtain high energy gains. These designs are robust to multimode asymmetries and are predicted to ignite even for significantly distorted implosions. Electron shock ignition requires tens of kilojoules of hot-e 's which can be produced only at a large laser facility like the National Ignition Facility, with the laser-to-hot-e conversion efficiency greater than 10% at laser intensities ˜1016 W /cm2 .

Electron Shock Ignition of Inertial Fusion Targets.

PubMed

Shang, W L; Betti, R; Hu, S X; Woo, K; Hao, L; Ren, C; Christopherson, A R; Bose, A; Theobald, W

2017-11-10

It is shown that inertial confinement fusion targets designed with low implosion velocities can be shock-ignited using laser-plasma interaction generated hot electrons (hot-e's) to obtain high energy gains. These designs are robust to multimode asymmetries and are predicted to ignite even for significantly distorted implosions. Electron shock ignition requires tens of kilojoules of hot-e's which can be produced only at a large laser facility like the National Ignition Facility, with the laser-to-hot-e conversion efficiency greater than 10% at laser intensities ∼10^{16}  W/cm^{2}.

Modeling Hohlraum-Based Laser Plasma Instability Experiments

NASA Astrophysics Data System (ADS)

Meezan, N. B.

2005-10-01

Laser fusion targets must control laser-plasma instabilities (LPI) in order to perform as designed. We present analyses of recent hohlraum LPI experiments from the Omega laser facility. The targets, gold hohlraums filled with gas or SiO2 foam, are preheated by several 3φ beams before an interaction beam (2φ or 3φ) is fired along the hohlraum axis. The experiments are simulated in 2-D and 3-D using the code hydra. The choice of electron thermal conduction model in hydra strongly affects the simulated plasma conditions. This work is part of a larger effort to systematically explore the usefulness of linear gain as a design tool for fusion targets. We find that the measured Raman and Brillouin backscatter scale monotonically with the peak linear gain calculated for the target; however, linear gain is not sufficient to explain all trends in the data. This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48.

Evaluation between residual stresses obtained by neutron diffraction and simulation for dual phase steel welded by laser process

NASA Astrophysics Data System (ADS)

Kouadri-Henni, Afia; Malard, Benoit

2018-05-01

This study aimed at characterizing the residual stresses (RS) distribution of a Dual Phase Steel (DP600) undergoing a Laser Beam Welding (LBW) with two different laser parameters. The RS in the ferritic phase have been experimentally determined by the use of the neutrons diffraction technique. The results confirmed a gradient of RS among different zones both on the top and below surfaces but also through the thickness of the fusion zone. Low compressive stresses were observed in the Base Metal (BM) close to the Heat Affected Zone (HAZ) whereas high tensile stresses were observed in the Fusion Zone (FZ). Numerical results showed a difference in the RS distribution depending on the model used. In the end, it appears that the high temperature gradient, specific to the laser beam, is the main factor governing the RS. Our results suggest as well that the approach regarding the RS should consider not only the temperature but also process parameters. When comparing simulation results with experimental data, the values converge well in some zones, in particular the FZ and the others less.

Fiber Laser Weldability of Austenitic Nickel Alloys

NASA Astrophysics Data System (ADS)

Watson, Jonathan

Recent developments of fiber lasers allow for easier beam delivery facilitating greater applications for laser welding in industry. Welding with high energy density heat sources allows for faster travel speeds, faster cooling rates, and smaller heat affected zones. However, there is a still a lack of knowledge base on how laser welding process parameters affect the weldability of austenitic nickel alloys. In this work, laser welds were made on several austenitic nickel alloys from different alloy families: HAYNESRTM 214RTM alloy, HAYNESRTM 282RTM alloy, HAYNESRTM 230RTM alloy, HAYNESRTM HR-120RTM alloy, HAYNESRTM HR-160 RTM alloy, HAYNESRTM 188 alloy, HAYNESRTM 718 alloy. Welds were made at 25 mm/s at laser powers ranging from 400 to 600 Watts. Solidification cracking was observed in cross-sections of the fusion zone of HR-160RTM alloy and HR-120RTM alloy. Dendritic solidification was found in all alloys, and partitioning within the dendritic structure compared well with Scheil calculations performed using ThermoCalc software. A eutectic liquid rich in carbide forming elements was found at the interdendritic regions in 188, 230RTM, 282 RTM, and 718 alloys and was quantified by processing backscatter electron images of the fusion zone. This interdendritic liquid was found to back fill solidification cracks that formed in the fusion zone during weldability testing. Transverse Varestraint and Sigma-Jig testing were performed to rank the weldability of alloys. During Transvarestraint testing, the ram drop timing was recorded in relation to the laser output, and a type R thermocouple was also placed in the laser path, and the approximate cooling rate of the fusion zone was recorded and used to calculate the solidification cracking temperature range. Rankings of the weldability compared well between Sigma-Jig and Transvarestraint testing, with the exception of 214 alloy and HR-120 alloy, which ranked much better and worse, respectively in Sigma-Jig tests. A possible explanation for this difference is the higher thermal conductivity and lower yields strength of 214 alloy and high temperatures, allowing it to accommodate more stress in the Sigma-Jig test. The final ranking of alloys from more weldable to less weldable by Sigma-Jig testing is 188, 214, 282, 718, 230, HR-120, and HR-160. The final ranking by maximum crack length in Transvarestraint specimens listed from more weldable to less weldable is: 188, 282, HR-120, 718, 230, 214, and HR-160.

Effect of Heat Input on the Tensile Damage Evolution in Pulsed Laser Welded Ti6Al4V Titanium Sheets

NASA Astrophysics Data System (ADS)

Liu, Jing; Gao, Xiaolong; Zhang, Jianxun

2016-11-01

The present paper is focused on studying the effect of heat input on the tensile damage evolution of pulsed Nd:YAG laser welding of Ti6Al4V alloy under monotonic loading. To analyze the reasons that the tensile fracture site of the pulsed-laser-welded Ti6Al4V sheet joints changes with the heat input under monotonic loading, the microstructure of the sample with different nominal strain values was investigated by in situ observation. Experiment results show that the tensile ductility and fatigue life of welded joints with low heat input are higher than that of welded joints with high heat input. Under tensile loads, the critical engineering strain for crack initiation is much lower in the welded joint with high heat input than in the welded joints with low and medium heat input. And the microstructural damage accumulation is much faster in the fusion zone than in the base metal for the welded joints with high input, whereas the microstructural damage accumulation is much faster in the base metal than in the fusion zone for the welded joints with low input. Consequently, the welded joints fractured in the fusion zone for the welds with high heat input, whereas the welded joints ruptured in the base metal for the welds with low heat input. It is proved that the fine grain microstructure produced by low heat input can improve the critical nominal strain for crack initiation and the resistance ability of microstructural damage.

Inertial-confinement fusion with lasers

NASA Astrophysics Data System (ADS)

Betti, R.; Hurricane, O. A.

2016-05-01

The quest for controlled fusion energy has been ongoing for over a half century. The demonstration of ignition and energy gain from thermonuclear fuels in the laboratory has been a major goal of fusion research for decades. Thermonuclear ignition is widely considered a milestone in the development of fusion energy, as well as a major scientific achievement with important applications in national security and basic sciences. The US is arguably the world leader in the inertial confinement approach to fusion and has invested in large facilities to pursue it, with the objective of establishing the science related to the safety and reliability of the stockpile of nuclear weapons. Although significant progress has been made in recent years, major challenges still remain in the quest for thermonuclear ignition via laser fusion. Here, we review the current state of the art in inertial confinement fusion research and describe the underlying physical principles.

Human Detection from a Mobile Robot Using Fusion of Laser and Vision Information

PubMed Central

Fotiadis, Efstathios P.; Garzón, Mario; Barrientos, Antonio

2013-01-01

This paper presents a human detection system that can be employed on board a mobile platform for use in autonomous surveillance of large outdoor infrastructures. The prediction is based on the fusion of two detection modules, one for the laser and another for the vision data. In the laser module, a novel feature set that better encapsulates variations due to noise, distance and human pose is proposed. This enhances the generalization of the system, while at the same time, increasing the outdoor performance in comparison with current methods. The vision module uses the combination of the histogram of oriented gradients descriptor and the linear support vector machine classifier. Current approaches use a fixed-size projection to define regions of interest on the image data using the range information from the laser range finder. When applied to small size unmanned ground vehicles, these techniques suffer from misalignment, due to platform vibrations and terrain irregularities. This is effectively addressed in this work by using a novel adaptive projection technique, which is based on a probabilistic formulation of the classifier performance. Finally, a probability calibration step is introduced in order to optimally fuse the information from both modules. Experiments in real world environments demonstrate the robustness of the proposed method. PMID:24008280

Human detection from a mobile robot using fusion of laser and vision information.

PubMed

Fotiadis, Efstathios P; Garzón, Mario; Barrientos, Antonio

2013-09-04

This paper presents a human detection system that can be employed on board a mobile platform for use in autonomous surveillance of large outdoor infrastructures. The prediction is based on the fusion of two detection modules, one for the laser and another for the vision data. In the laser module, a novel feature set that better encapsulates variations due to noise, distance and human pose is proposed. This enhances the generalization of the system, while at the same time, increasing the outdoor performance in comparison with current methods. The vision module uses the combination of the histogram of oriented gradients descriptor and the linear support vector machine classifier. Current approaches use a fixed-size projection to define regions of interest on the image data using the range information from the laser range finder. When applied to small size unmanned ground vehicles, these techniques suffer from misalignment, due to platform vibrations and terrain irregularities. This is effectively addressed in this work by using a novel adaptive projection technique, which is based on a probabilistic formulation of the classifier performance. Finally, a probability calibration step is introduced in order to optimally fuse the information from both modules. Experiments in real world environments demonstrate the robustness of the proposed method.

Method for selecting hollow microspheres for use in laser fusion targets

DOEpatents

Farnum, Eugene H.; Fries, R. Jay; Havenhill, Jerry W.; Smith, Maurice Lee; Stoltz, Daniel L.

1976-01-01

Hollow microspheres having thin and very uniform wall thickness are useful as containers for the deuterium and tritium gas mixture used as a fuel in laser fusion targets. Hollow microspheres are commercially available; however, in commercial lots only a very small number meet the rigid requirements for use in laser fusion targets. Those meeting these requirements may be separated from the unsuitable ones by subjecting the commercial lot to size and density separations and then by subjecting those hollow microspheres thus separated to an external pressurization at which those which are aspherical or which have nonuniform walls are broken and separating the sound hollow microspheres from the broken ones.

220 microJ Monolithic Single-Frequency Q-switched Fiber Laser at 2 micrometers by Using Highly Tm-doped Germanate Fibers

DTIC Science & Technology

2011-09-15

actively Q-switching all-fiber lasers include mag- netostriction modulation of fiber Bragg gratings ( FBGs ), stretching of FBGs with piezoelectric...report an all- fiber single-frequency actively Q-switched laser operat- ing at ∼1920 nm by using a piezo to press the fiber in the FBG cavity based on...fusion-spliced between two FBGs as shown in Fig. 1. One FBG has a high reflectivity (HR) grating imprinted on a non-PM silica fiber. The other FBG

Laser prospects for SPS and restoration of the ozone layer

NASA Technical Reports Server (NTRS)

Kruzhilin, Yuri

1992-01-01

Large-scale applications of high-power lasers are considered (special experiments are described to confirm the feasibility of these applications) to achieve also large-scale environmental advantages. The possibility of producing electric energy by Laser-Solar Power Satellites in the near future is discussed. A full-scale experimental L-SPS satellite is suggested as a module of a global space energy network. Electric power of about 10 MW at the surface of the Earth is achievable as a result of energy conversion of laser radiation. L-SPS is based on the greatest advantages of present optics and laser techniques. Specialized-scale experiments are carried out and described. L-SPS project could provide real electricity for consumers not later than by highly developed fusion techniques, and the environmental aftereffects are quite favorable. A new method of power supply for satellites is suggested, based on the connection of an on-board electric circuit directly with the ground-based power grid by means of laser beams.

Fusion reactor pumped laser

DOEpatents

Jassby, D.L.

1987-09-04

A nuclear pumped laser capable of producing long pulses of very high power laser radiation is provided. A toroidal fusion reactor provides energetic neutrons which are slowed down by a moderator. The moderated neutrons are converted to energetic particles capable of pumping a lasing medium. The lasing medium is housed in an annular cell surrounding the reactor. The cell includes an annular reflecting mirror at the bottom and an annular output window at the top. A neutron reflector is disposed around the cell to reflect escaping neutrons back into the cell. The laser radiation from the annular window is focused onto a beam compactor which generates a single coherent output laser beam. 10 figs.

Fusion reactor pumped laser

DOEpatents

Jassby, Daniel L.

1988-01-01

A nuclear pumped laser capable of producing long pulses of very high power laser radiation is provided. A toroidal fusion reactor provides energetic neutrons which are slowed down by a moderator. The moderated neutrons are converted to energetic particles capable of pumping a lasing medium. The lasing medium is housed in an annular cell surrounding the reactor. The cell includes an annular reflecting mirror at the bottom and an annular output window at the top. A neutron reflector is disposed around the cell to reflect escaping neutrons back into the cell. The laser radiation from the annular window is focused onto a beam compactor which generates a single coherent output laser beam.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kanesue, Takeshi; Ikeda, Shunsuke

A laser ion source is a promising candidate as an ion source for heavy ion inertial fusion (HIF), where a pulsed ultra-intense and low-charged heavy ion beam is required. It is a key development for a laser ion source to transport laser-produced plasma with a magnetic field to achieve a high current beam. The effect of a tapered magnetic field on laser produced plasma is demonstrated by comparing the results with a straight solenoid magnet. The magnetic field of interest is a wider aperture on a target side and narrower aperture on an extraction side. Furthermore, based on the experimentallymore » obtained results, the performance of a scaled laser ion source for HIF was estimated.« less

Editorially Speaking - Fusion Power: Reasons for Higher Priority

ERIC Educational Resources Information Center

Lippincott, William T.

1973-01-01

Discusses current research trends in the use of laser-fusion technology in combustion chambers to eradicate energy shortages. Indicates that fusion power could be made available at a relatively low expense. (CC)

Fusion Studies in Japan

NASA Astrophysics Data System (ADS)

Ogawa, Yuichi

2016-05-01

A new strategic energy plan decided by the Japanese Cabinet in 2014 strongly supports the steady promotion of nuclear fusion development activities, including the ITER project and the Broader Approach activities from the long-term viewpoint. Atomic Energy Commission (AEC) in Japan formulated the Third Phase Basic Program so as to promote an experimental fusion reactor project. In 2005 AEC has reviewed this Program, and discussed on selection and concentration among many projects of fusion reactor development. In addition to the promotion of ITER project, advanced tokamak research by JT-60SA, helical plasma experiment by LHD, FIREX project in laser fusion research and fusion engineering by IFMIF were highly prioritized. Although the basic concept is quite different between tokamak, helical and laser fusion researches, there exist a lot of common features such as plasma physics on 3-D magnetic geometry, high power heat load on plasma facing component and so on. Therefore, a synergetic scenario on fusion reactor development among various plasma confinement concepts would be important.

Microstructure and Porosity of Laser Welds in Cast Ti-6Al-4V with Addition of Boron

NASA Astrophysics Data System (ADS)

Tolvanen, Sakari; Pederson, Robert; Klement, Uta

2018-03-01

Addition of small amounts of boron to cast Ti-6Al-4V alloy has shown to render a finer microstructure and improved mechanical properties. For such an improved alloy to be widely applicable for large aerospace structural components, successful welding of such castings is essential. In the present work, the microstructure and porosity of laser welds in a standard grade cast Ti-6Al-4V alloy as well as two modified alloy versions with different boron concentrations have been investigated. Prior-β grain reconstruction revealed the prior-β grain structure in the weld zones. In fusion zones of the welds, boron was found to refine the grain size significantly and rendered narrow elongated grains. TiB particles in the prior-β grain boundaries in the cast base material restricted grain growth in the heat-affected zone. The TiB particles that existed in the as cast alloys decreased in size in the fusion zones of welds. The hardness in the weld zones was higher than in the base material and boron did not have a significant effect on hardness of the weld zones. The fusion zones were smaller in the boron-modified alloys as compared with Ti-6Al-4V without boron. Computed tomography X-ray investigations of the laser welds showed that pores in the FZ of the boron modified alloys were confined to the lower part of the welds, suggesting that boron addition influences melt pool flow.

Laser heating challenges of high yield MagLIF targets

NASA Astrophysics Data System (ADS)

Slutz, Stephen; Sefkow, Adam; Vesey, Roger

2014-10-01

The MagLIF (Magnetized Liner Inertial Fusion) concept is predicted by numerical simulation to produce fusion yields of about 100 kJ, when driven by 25 MA from the existing Z accelerator [S. A. Slutz et al. Phys. Plasmas 17, 056303 (2010)] and much higher yields with future accelerators delivering higher currents [Slutz and Vesey PRL 108, 025003 (2012)]. The fuel must be heated before compression to obtain significant fusion yields due to the relatively slow implosion velocities (~ 100 km/s) of magnetically driven liners. Lasers provide a convenient means to accomplish this pre-compressional heating of the fusion fuel, but there are challenges. The laser must penetrate a foil covering the laser entrance hole and deposit 20-30 kJ within the ~1 cm length of the liner in fuel at 6-12 mg/cc. Such high densities could result in beam scattering due to refraction and laser plasma interactions. Numerical simulations of the laser heating process are presented, which indicate that energies as high as 30 kJ could be deposited in the fuel by using two laser pulses of different wavelengths. Simulations of this process will be presented as well of results for a MagLIF design for a potential new machine delivering 50 MA of current. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

Mathematical modelling and linear stability analysis of laser fusion cutting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hermanns, Torsten; Schulz, Wolfgang; Vossen, Georg

A model for laser fusion cutting is presented and investigated by linear stability analysis in order to study the tendency for dynamic behavior and subsequent ripple formation. The result is a so called stability function that describes the correlation of the setting values of the process and the process’ amount of dynamic behavior.

LLE Review 116 (July-September 2008)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marozas, J.A., editor

2010-03-12

This issue has the following articles: (1) Optimizing Electron-Positron Pair Production on kJ-Class High-Intensity Lasers for the Purpose of Pair-Plasma Creation; (2) Neutron Yield Study of Direct-Drive, Low-Adiabat Cryogenic D2 Implosions on OMEGA; (3) Al 1s-2p Absorption Spectroscopy of Shock-Wave Heating and Compression in Laser-Driven Planar Foil; (4) A Measurable Lawson Criterion and Hydro-Equivalent Curves for Inertial Confinement Fusion; (5) Pulsed-THz Characterization of Hg-Based, High-Temperature Superconductors; (6) LLE's Summer High School Research Program; (7) FY08 Laser Facility Report; and (8) National Laser Users Facility and External Users Programs.

Deformation behavior of laser welds in high temperature oxidation resistant Fe-Cr-Al alloys for fuel cladding applications

NASA Astrophysics Data System (ADS)

Field, Kevin G.; Gussev, Maxim N.; Yamamoto, Yukinori; Snead, Lance L.

2014-11-01

Ferritic-structured Fe-Cr-Al alloys are being developed and show promise as oxidation resistant accident tolerant light water reactor fuel cladding. This study focuses on investigating the weldability and post-weld mechanical behavior of three model alloys in a range of Fe-(13-17.5)Cr-(3-4.4)Al (wt.%) with a minor addition of yttrium using modern laser-welding techniques. A detailed study on the mechanical performance of bead-on-plate welds using sub-sized, flat dog-bone tensile specimens and digital image correlation (DIC) has been carried out to determine the performance of welds as a function of alloy composition. Results indicated a reduction in the yield strength within the fusion zone compared to the base metal. Yield strength reduction was found to be primarily constrained to the fusion zone due to grain coarsening with a less severe reduction in the heat affected zone. For all proposed alloys, laser welding resulted in a defect free weld devoid of cracking or inclusions.

Time-resolved compression of a capsule with a cone to high density for fast-ignition laser fusion

DOE PAGES

Theobald, W.; Solodov, A. A.; Stoeckl, C.; ...

2014-12-12

The advent of high-intensity lasers enables us to recreate and study the behaviour of matter under the extreme densities and pressures that exist in many astrophysical objects. It may also enable us to develop a power source based on laser-driven nuclear fusion. Achieving such conditions usually requires a target that is highly uniform and spherically symmetric. Here we show that it is possible to generate high densities in a so-called fast-ignition target that consists of a thin shell whose spherical symmetry is interrupted by the inclusion of a metal cone. Using picosecond-time-resolved X-ray radiography, we show that we can achievemore » areal densities in excess of 300 mg cm -2 with a nanosecond-duration compression pulse -- the highest areal density ever reported for a cone-in-shell target. Such densities are high enough to stop MeV electrons, which is necessary for igniting the fuel with a subsequent picosecond pulse focused into the resulting plasma.« less

Time-resolved compression of a capsule with a cone to high density for fast-ignition laser fusion.

PubMed

Theobald, W; Solodov, A A; Stoeckl, C; Anderson, K S; Beg, F N; Epstein, R; Fiksel, G; Giraldez, E M; Glebov, V Yu; Habara, H; Ivancic, S; Jarrott, L C; Marshall, F J; McKiernan, G; McLean, H S; Mileham, C; Nilson, P M; Patel, P K; Pérez, F; Sangster, T C; Santos, J J; Sawada, H; Shvydky, A; Stephens, R B; Wei, M S

2014-12-12

The advent of high-intensity lasers enables us to recreate and study the behaviour of matter under the extreme densities and pressures that exist in many astrophysical objects. It may also enable us to develop a power source based on laser-driven nuclear fusion. Achieving such conditions usually requires a target that is highly uniform and spherically symmetric. Here we show that it is possible to generate high densities in a so-called fast-ignition target that consists of a thin shell whose spherical symmetry is interrupted by the inclusion of a metal cone. Using picosecond-time-resolved X-ray radiography, we show that we can achieve areal densities in excess of 300 mg cm(-2) with a nanosecond-duration compression pulse--the highest areal density ever reported for a cone-in-shell target. Such densities are high enough to stop MeV electrons, which is necessary for igniting the fuel with a subsequent picosecond pulse focused into the resulting plasma.

Conference Grant Proposal for ICOPS 2016

DOE Office of Scientific and Technical Information (OSTI.GOV)

Safronova, Alla

ICOPS (International Conference on Plasma Science) is an internationally renowned, well-attended annual conference that involves topics of direct interest to the Office of Fusion Energy Sciences of Department of Energy. In particular, ICOPS 2016 emphasized both the traditional areas of plasma science and the new areas of growth that include but are not limited to Fusion (Inertial, Magnetic and Alternate Concepts), Particle Acceleration with Laser and Beams, High Energy Density Matter, Laser Produced Plasma, Fast Z-pinches, Computational Plasma Physics, Plasma Diagnostics, and such frontiers as studying Warm Dense Matter using the X-ray free electron lasers. The travel support of themore » students at ICOPS comes usually from sponsor organizations. Increasing the participation of outstanding students at ICOPS 2016 who are the first authors of the abstracts and are selected to receive the travel support based on the scientific merit of the submitted abstracts is crucial for the creation of the new generation of the plasma physicists.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hellemans, A.

Space beam weapons and unlimited energy from fusion may have been pipe dreams of the 1980s. But today these dreams are giving birth to practical laboratory tools: tabletop x-ray lasers that may open up whole new areas of chemistry and biology. The first x-ray lasers were energized by nuclear explosions or jolts of light from giant glass lasers built for fusion experiments-hardly bench-top equipment. Now, says Joseph Nilsen, a physicist at Lawrence Livermore National Laboratory (LLNL), {open_quotes}several small university-size places are actually making a lot of progress toward tabletop lasers people can use every day.{close_quotes} This article highlight progress towardsmore » cheap ubiquitous X-ray lasers as described at the 5th International Conference on X-ray Lasers.« less

Mechanical and Fatigue Properties of Additively Manufactured Metallic Materials

NASA Astrophysics Data System (ADS)

Yadollahi, Aref

This study aims to investigate the mechanical and fatigue behavior of additively manufactured metallic materials. Several challenges associated with different metal additive manufacturing (AM) techniques (i.e. laser-powder bed fusion and direct laser deposition) have been addressed experimentally and numerically. Experiments have been carried out to study the effects of process inter-layer time interval--i.e. either building the samples one-at-a-time or multi-at-a-time (in-parallel)--on the microstructural features and mechanical properties of 316L stainless steel samples, fabricated via a direct laser deposition (DLD). Next, the effect of building orientation--i.e. the orientation in which AM parts are built--on microstructure, tensile, and fatigue behaviors of 17-4 PH stainless steel, fabricated via a laser-powder bed fusion (L-PBF) method was investigated. Afterwards, the effect of surface finishing--here, as-built versus machined--on uniaxial fatigue behavior and failure mechanisms of Inconel 718 fabricated via a laser-powder bed fusion technique was sought. The numerical studies, as part of this dissertation, aimed to model the mechanical behavior of AM materials, under monotonic and cyclic loading, based on the observations and findings from the experiments. Despite significant research efforts for optimizing process parameters, achieving a homogenous, defect-free AM product--immediately after fabrication--has not yet been fully demonstrated. Thus, one solution for ensuring the adoption of AM materials for application should center on predicting the variations in mechanical behavior of AM parts based on their resultant microstructure. In this regard, an internal state variable (ISV) plasticity-damage model was employed to quantify the damage evolution in DLD 316L SS, under tensile loading, using the microstructural features associated with the manufacturing process. Finally, fatigue behavior of AM parts has been modeled based on the crack-growth concept. Using the FASTRAN code, the fatigue-life of L-PBF Inconel 718 was accurately calculated using the size and shape of process-induced voids in the material. In addition, the maximum valley depth of the surface profile was found to be an appropriate representative of the initial surface flaw for fatigue-life prediction of AM materials in an as-built surface condition.

Performance and economics analysis of several laser fusion breeder fueled electricity generation systems

NASA Astrophysics Data System (ADS)

Berwald, D. H.; Maniscalco, J. A.

1981-01-01

The paper evaluates the potential of several future electricity generating systems composed of laser fusion-driven breeder reactors that provide fissile fuel for current technology light water fission power reactors (LWRs). The performance and economic feasibility of four fusion breeder blanket technologies for laser fusion drivers, namely uranium fast fission (UFF) blankets, uranium-thorium fast fission (UTFF) blankets, thorium fast fission (TFF) blankets and thorium-suppressed fission (TSF) blankets, are considered, including design and costs of two kinds, fixed (indirect) costs associated with plant capital and variable (direct) costs associated with fuel processing and operation and maintenance. Results indicate that the UTFF and TFF systems produce electricity most inexpensively and that any of the four breeder blanket concepts, including the TSF and UFF systems, can produce electricity for about 25 to 33% above the cost of electricity produced by a new LWR operating on the current once-through cycle. It is suggested that fusion breeders could supply most or all of our fissile fuel makeup requirements within about 20 years after commercial introduction.

PHYSICS: Will Livermore Laser Ever Burn Brightly?

PubMed

Seife, C; Malakoff, D

2000-08-18

The National Ignition Facility (NIF), a superlaser being built here at Lawrence Livermore National Laboratory in an effort to use lasers rather than nuclear explosions to create a fusion reaction, is supposed to allow weapons makers to preserve the nuclear arsenal--and do nifty fusion science, too. But a new report that examines its troubled past also casts doubt on its future. Even some of NIF's scientific and political allies are beginning to talk openly of a scaled-down version of the original 192-laser design.

Nuclear science experiments with a bright neutron source from fusion reactions on the OMEGA Laser System

NASA Astrophysics Data System (ADS)

Forrest, C. J.; Knauer, J. P.; Schroeder, W. U.; Glebov, V. Yu.; Radha, P. B.; Regan, S. P.; Sangster, T. C.; Sickles, M.; Stoeckl, C.; Szczepanski, J.

2018-04-01

Subnanosecond impulses of 1013 to 1014 neutrons, produced in direct-drive laser inertial confinement fusion implosions, have been used to irradiate deuterated targets at the OMEGA Laser System (Boehly et al., 1997). The target compounds include heavy water (D2O) and deuterated benzene (C6D6). Yields and energy spectra of neutrons from D(n,2n)p to study the breakup reaction have been measured at a forward angle of θlab = 3 .5∘ ± 3.5° with a sensitive, high-dynamic-range neutron time-of-flight spectrometer to infer the double-differential breakup cross section d2 σ/dE d Ω for 14-MeV D-T fusion neutrons.

Fusion pumped laser

DOEpatents

Pappas, D.S.

1987-07-31

The apparatus of this invention may comprise a system for generating laser radiation from a high-energy neutron source. The neutron source is a tokamak fusion reactor generating a long pulse of high-energy neutrons and having a temperature and magnetic field effective to generate a neutron flux of at least 10/sup 15/ neutrons/cm/sup 2//center dot/s. Conversion means are provided adjacent the fusion reactor at a location operable for converting the high-energy neutrons to an energy source with an intensity and energy effective to excite a preselected lasing medium. A lasing medium is spaced about and responsive to the energy source to generate a population inversion effective to support laser oscillations for generating output radiation. 2 figs., 2 tabs.

Laser or charged-particle-beam fusion reactor with direct electric generation by magnetic flux compression

DOEpatents

Lasche, George P.

1988-01-01

A high-power-density laser or charged-particle-beam fusion reactor system maximizes the directed kinetic energy imparted to a large mass of liquid lithium by a centrally located fusion target. A fusion target is embedded in a large mass of lithium, of sufficient radius to act as a tritium breeding blanket, and provided with ports for the access of beam energy to implode the target. The directed kinetic energy is converted directly to electricity with high efficiency by work done against a pulsed magnetic field applied exterior to the lithium. Because the system maximizes the blanket thickness per unit volume of lithium, neutron-induced radioactivities in the reaction chamber wall are several orders of magnitude less than is typical of other fusion reactor systems.

Laser or charged-particle-beam fusion reactor with direct electric generation by magnetic flux compression

DOEpatents

Lasche, G.P.

1987-02-20

A high-power-density-laser or charged-particle-beam fusion reactor system maximizes the directed kinetic energy imparted to a large mass of liquid lithium by a centrally located fusion target. A fusion target is embedded in a large mass of lithium, of sufficient radius to act as a tritium breeding blanket, and provided with ports for the access of beam energy to implode the target. The directed kinetic energy is converted directly to electricity with high efficiency by work done against a pulsed magnetic field applied exterior to the lithium. Because the system maximizes the blanket thickness per unit volume of lithium, neutron-induced radioactivities in the reaction chamber wall are several orders of magnitude less than is typical of other fusion reactor systems. 25 figs.

Surface texture and hardness of dental alloys processed by alternative technologies

NASA Astrophysics Data System (ADS)

Porojan, Liliana; Savencu, Cristina E.; Topală, Florin I.; Porojan, Sorin D.

2017-08-01

Technological developments have led to the implementation of novel digitalized manufacturing methods for the production of metallic structures in prosthetic dentistry. These technologies can be classified as based on subtractive manufacturing, assisted by computer-aided design/computer-aided manufacturing (CAD/CAM) systems, or on additive manufacturing (AM), such as the recently developed laser-based methods. The aim of the study was to assess the surface texture and hardness of metallic structures for dental restorations obtained by alternative technologies: conventional casting (CST), computerized milling (MIL), AM power bed fusion methods, respective selective laser melting (SLM) and selective laser sintering (SLS). For the experimental analyses metallic specimens made of Co-Cr dental alloys were prepared as indicated by the manufacturers. The specimen structure at the macro level was observed by an optical microscope and micro-hardness was measured in all substrates. Metallic frameworks obtained by AM are characterized by increased hardness, depending also on the surface processing. The formation of microstructural defects can be better controlled and avoided during SLM and MIL process. Application of power bed fusion techniques, like SLS and SLM, is currently a challenge in dental alloys processing.

Laser-fusion targets for reactors

DOEpatents

Nuckolls, John H.; Thiessen, Albert R.

1987-01-01

A laser target comprising a thermonuclear fuel capsule composed of a centrally located quantity of fuel surrounded by at least one or more layers or shells of material for forming an atmosphere around the capsule by a low energy laser prepulse. The fuel may be formed as a solid core or hollow shell, and, under certain applications, a pusher-layer or shell is located intermediate the fuel and the atmosphere forming material. The fuel is ignited by symmetrical implosion via energy produced by a laser, or other energy sources such as an electron beam machine or ion beam machine, whereby thermonuclear burn of the fuel capsule creates energy for applications such as generation of electricity via a laser fusion reactor.

Review of controlled fusion research using laser heating.

NASA Technical Reports Server (NTRS)

Hertzberg, A.

1973-01-01

Development of methods for generating high laser pulse energy has stimulated research leading to new ideas for practical controlled thermonuclear fusion machines. A review is presented of some important efforts in progress, and two different approaches have been selected as examples for discussion. One involves the concept of very short pulse lasers with power output tailored, in time, to obtain a nearly isentropic compression of a deuterium-tritium pellet to very high densities and temperatures. A second approach utilizing long wavelength, long pulse, efficient gas lasers to heat a column of plasma contained in a solenoidal field is also discussed. The working requirements of the laser and various magnetic field geometries of this approach are described.

Block Ignition Inertial Confinement Fusion (ICF) with Condensed Matter Cluster Type Targets for p-B11 Powered Space Propulsion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miley, George H.; Hora, H.; Badziak, J.

The use of laser-driven Inertial Confinement Fusion (ICF) for space propulsion has been the subject of several earlier conceptual design studies, (see: Orth, 1998; and other references therein). However, these studies were based on older ICF technology using either 'direct' or 'in-direct x-ray driven' type target irradiation. Important new directions have opened for laser ICF in recent years following the development of 'chirped' lasers capable of ultra short pulses with powers of TW up to few PW which leads to the concept of 'fast ignition (FI)' to achieve higher energy gains from target implosions. In a recent publication the authorsmore » showed that use of a modified type of FI, termed 'block ignition' (Miley et al., 2008), could meet many of the requirements anticipated (but not then available) by the designs of the Vehicle for Interplanetary Space Transport Applications (VISTA) ICF fusion propulsion ship (Orth, 2008) for deep space missions. Subsequently the first author devised and presented concepts for imbedding high density condensed matter 'clusters' of deuterium into the target to obtain ultra high local fusion reaction rates (Miley, 2008). Such rates are possible due to the high density of the clusters (over an order of magnitude above cryogenic deuterium). Once compressed by the implosion, the yet higher density gives an ultra high reaction rate over the cluster volume since the fusion rate is proportional to the square of the fuel density. Most recently, a new discovery discussed here indicates that the target matrix could be composed of B{sup 11} with proton clusters imbedded. This then makes p-B{sup 11} fusion practical, assuming all of the physics issues such as stability of the clusters during compression are resolved. Indeed, p-B{sup 11} power is ideal for fusion propulsion since it has a minimum of unwanted side products while giving most of the reaction energy to energetic alpha particles which can be directed into an exhaust (propulsion) nozzle. Power plants using p-B{sup 11} have been discussed for such applications before, but prior designs face formidable physics/technology issues, largely overcome with the present approach.« less

Shock ignition: a new approach to high gain inertial confinement fusion on the national ignition facility.

PubMed

Perkins, L J; Betti, R; LaFortune, K N; Williams, W H

2009-07-24

Shock ignition, an alternative concept for igniting thermonuclear fuel, is explored as a new approach to high gain, inertial confinement fusion targets for the National Ignition Facility (NIF). Results indicate thermonuclear yields of approximately 120-250 MJ may be possible with laser drive energies of 1-1.6 MJ, while gains of approximately 50 may still be achievable at only approximately 0.2 MJ drive energy. The scaling of NIF energy gain with laser energy is found to be G approximately 126E (MJ);{0.510}. This offers the potential for high-gain targets that may lead to smaller, more economic fusion power reactors and a cheaper fusion energy development path.

A comparative evaluation of laser and GTA welds in a high-strength titanium alloy -- Ti-6-22-22S

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baeslack, W.A. III; Hurley, J.; Paskell, T.

1994-12-31

Titanium alloy Ti-6Al-2Sn-2Zr-2Mo-2Cr-025Si (hereafter designated Ti-6-22-22S)is an alpha-beta titanium alloy developed for deep hardenability, high strength, intermediate temperature creep resistance, and moderate toughness. As a potential structural material for next-generation aircraft and aerospace systems, the weldability of Ti-6-22-22S has recently become a subject of increasing importance and concern. In the welding of titanium sheet, achieving satisfactory ductility is the principal limitation to alloy weldability, with poor ductility promoted by a coarse beta grain structure in the weld fusion and near-heat-affected zones. Square-butt welds were produced in 1.6 mm thick Ti-6-22-22S sheet using automatic GTA and CO{sub 2} laser welding systems.more » Microstructure analysis and DPH hardness traverses were performed on mounted. polished and etched specimens. Three-point bend and tensile tests were performed on transverse-weld and longitudinal-weld oriented specimens. Microstructure analysis of the laser welds revealed a fine, columnar fusion zone beta grain macrostructure and a fully-martensitic transformed-beta microstructure. Consistent with the microstructural similarities, fusion zone hardnesses of the laser welds were comparable (385 and 390 DPG, respectively) and greater than that of the base metal (330 DPH). In general, laser welds did not exhibit markedly superior ductilities relative to the GTAW, which was attributed to differences in the nature of the intragranular transformed-beta microstructures, being coarser and softer for the GTAW, the response of these as-welded microstructures to heat treatment, and interactions between the transformed-beta microstructure and the beta grain macrostructure.« less

Additive Manufacturing of Nickel-Base Superalloy IN100 Through Scanning Laser Epitaxy

NASA Astrophysics Data System (ADS)

Basak, Amrita; Das, Suman

2018-01-01

Scanning laser epitaxy (SLE) is a laser powder bed fusion (LPBF)-based additive manufacturing process that uses a high-power laser to consolidate metal powders facilitating the fabrication of three-dimensional objects. In the present study, SLE is used to produce samples of IN100, a high-γ' non-weldable nickel-base superalloy on similar chemistry substrates. A thorough analysis is performed using various advanced material characterization techniques such as high-resolution optical microscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy, and Vickers microhardness measurements to characterize and compare the quality of the SLE-fabricated IN100 deposits with the investment cast IN100 substrates. The results show that the IN100 deposits have a finer γ/γ' microstructure, weaker elemental segregation, and higher microhardness compared with the substrate. Through this study, it is demonstrated that the SLE process has tremendous potential in the repair and manufacture of gas turbine hot-section components.

The national ignition facility high-energy ultraviolet laser system

NASA Astrophysics Data System (ADS)

Moses, Edward I.

2004-09-01

The National Ignition Facility (NIF), currently under construction at the Lawrence Livermore National Laboratory, is a stadium-sized facility containing a 192-beam, 1.8 MJ, 500 TW, ultraviolet laser system together with a 10-m diameter target chamber with room for nearly 100 experimental diagnostics. When completed, NIF will be the world's largest and most energetic laser experimental system, providing an international center to study inertial confinement fusion and the physics of matter at extreme energy densities and pressures. NIF's 192 energetic laser beams will compress fusion targets to conditions required for thermonuclear burn, liberating more energy than required to initiate the fusion reactions. Other NIF experiments will allow the study of physical processes at temperatures approaching 10 8 K and 10 11 Bar, conditions that exist naturally only in the interior of stars, planets and in nuclear weapons. NIF is now entering the first phases of its laser commissioning program. The first four beams of the NIF laser system have generated 106 kJ of infrared light and over 10 kJ at the third harmonic (351 nm). NIF's target experimental systems are also being installed in preparation for experiments to begin in late 2003. This paper provides a detailed look the NIF laser systems, the significant laser and optical systems breakthroughs that were developed, the results of recent laser commissioning shots, and plans for commissioning diagnostics for experiments on NIF.

Continuous and pulsed laser high power beam combiner for additive manufacturing applications

NASA Astrophysics Data System (ADS)

Bassignana, Marta; Califano, Alessio; Pescarmona, Francesco; Braglia, Andrea; Perrone, Guido

2018-02-01

Laser-based additive manufacturing (AM) from metal powders is emerging as the new industrial revolution, although current fabrication approaches still require long mechanical post-processing to improve the final surface quality and meet the design tolerances. To overcome this limitation, the next generation machines are expected to complement laser AM with laser ablation (LA) to implement surface finishing and micro texturing already during the device growth process. With this aim, a new beam combiner to allow the real-time interchange of additive and subtractive processes using the same scanner head has been designed. Extensive tests have been carried out using a 6 kW continuous-wave laser similar to that used for the metal powder fusion and a nanosecond 100W pulsed source similar to that used for laser ablation.

Evolution of Gas Cell Targets for Magnetized Liner Inertial Fusion Experiments at the Sandia National Laboratories PECOS Test Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paguio, R. R.; Smith, G. E.; Taylor, J. L.

Z-Beamlet (ZBL) experiments conducted at the PECOS test facility at Sandia National Laboratories (SNL) investigated the nonlinear processes in laser plasma interaction (or laserplasma instabilities LPI) that complicate the deposition of laser energy by enhanced absorption, backscatter, filamentation and beam-spray that can occur in large-scale laser-heated gas cell targets. These targets and experiments were designed to provide better insight into the physics of the laser preheat stage of the Magnetized Liner Inertial Fusion (MagLIF) scheme being tested on the SNL Z-machine. The experiments aim to understand the tradeoffs between laser spot size, laser pulse shape, laser entrance hole (LEH) windowmore » thickness, and fuel density for laser preheat. Gas cell target design evolution and fabrication adaptations to accommodate the evolving experiment and scientific requirements are also described in this paper.« less

Evolution of Gas Cell Targets for Magnetized Liner Inertial Fusion Experiments at the Sandia National Laboratories PECOS Test Facility

DOE PAGES

Paguio, R. R.; Smith, G. E.; Taylor, J. L.; ...

2017-12-04

Z-Beamlet (ZBL) experiments conducted at the PECOS test facility at Sandia National Laboratories (SNL) investigated the nonlinear processes in laser plasma interaction (or laserplasma instabilities LPI) that complicate the deposition of laser energy by enhanced absorption, backscatter, filamentation and beam-spray that can occur in large-scale laser-heated gas cell targets. These targets and experiments were designed to provide better insight into the physics of the laser preheat stage of the Magnetized Liner Inertial Fusion (MagLIF) scheme being tested on the SNL Z-machine. The experiments aim to understand the tradeoffs between laser spot size, laser pulse shape, laser entrance hole (LEH) windowmore » thickness, and fuel density for laser preheat. Gas cell target design evolution and fabrication adaptations to accommodate the evolving experiment and scientific requirements are also described in this paper.« less

The Complete Burning of Weapons Grade Plutonium and Highly Enriched Uranium with (Laser Inertial Fusion-Fission Energy) LIFE Engine

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farmer, J C; Diaz de la Rubia, T; Moses, E

2008-12-23

The National Ignition Facility (NIF) project, a laser-based Inertial Confinement Fusion (ICF) experiment designed to achieve thermonuclear fusion ignition and burn in the laboratory, is under construction at the Lawrence Livermore National Laboratory (LLNL) and will be completed in April of 2009. Experiments designed to accomplish the NIF's goal will commence in late FY2010 utilizing laser energies of 1 to 1.3 MJ. Fusion yields of the order of 10 to 20 MJ are expected soon thereafter. Laser initiated fusion-fission (LIFE) engines have now been designed to produce nuclear power from natural or depleted uranium without isotopic enrichment, and from spentmore » nuclear fuel from light water reactors without chemical separation into weapons-attractive actinide streams. A point-source of high-energy neutrons produced by laser-generated, thermonuclear fusion within a target is used to achieve ultra-deep burn-up of the fertile or fissile fuel in a sub-critical fission blanket. Fertile fuels including depleted uranium (DU), natural uranium (NatU), spent nuclear fuel (SNF), and thorium (Th) can be used. Fissile fuels such as low-enrichment uranium (LEU), excess weapons plutonium (WG-Pu), and excess highly-enriched uranium (HEU) may be used as well. Based upon preliminary analyses, it is believed that LIFE could help meet worldwide electricity needs in a safe and sustainable manner, while drastically shrinking the nation's and world's stockpile of spent nuclear fuel and excess weapons materials. LIFE takes advantage of the significant advances in laser-based inertial confinement fusion that are taking place at the NIF at LLNL where it is expected that thermonuclear ignition will be achieved in the 2010-2011 timeframe. Starting from as little as 300 to 500 MW of fusion power, a single LIFE engine will be able to generate 2000 to 3000 MWt in steady state for periods of years to decades, depending on the nuclear fuel and engine configuration. Because the fission blanket in a fusion-fission hybrid system is subcritical, a LIFE engine can burn any fertile or fissile nuclear material, including unenriched natural or depleted U and SNF, and can extract a very high percentage of the energy content of its fuel resulting in greatly enhanced energy generation per metric ton of nuclear fuel, as well as nuclear waste forms with vastly reduced concentrations of long-lived actinides. LIFE engines could thus provide the ability to generate vast amounts of electricity while greatly reducing the actinide content of any existing or future nuclear waste and extending the availability of low cost nuclear fuels for several thousand years. LIFE also provides an attractive pathway for burning excess weapons Pu to over 99% FIMA (fission of initial metal atoms) without the need for fabricating or reprocessing mixed oxide fuels (MOX). Because of all of these advantages, LIFE engines offer a pathway toward sustainable and safe nuclear power that significantly mitigates nuclear proliferation concerns and minimizes nuclear waste. An important aspect of a LIFE engine is the fact that there is no need to extract the fission fuel from the fission blanket before it is burned to the desired final level. Except for fuel inspection and maintenance process times, the nuclear fuel is always within the core of the reactor and no weapons-attractive materials are available outside at any point in time. However, an important consideration when discussing proliferation concerns associated with any nuclear fuel cycle is the ease with which reactor fuel can be converted to weapons usable materials, not just when it is extracted as waste, but at any point in the fuel cycle. Although the nuclear fuel remains in the core of the engine until ultra deep actinide burn up is achieved, soon after start up of the engine, once the system breeds up to full power, several tons of fissile material is present in the fission blanket. However, this fissile material is widely dispersed in millions of fuel pebbles, which can be tagged as individual accountable items, and thus made difficult to divert in large quantities. This report discusses the application of the LIFE concept to nonproliferation issues, initially looking at the LIFE (Laser Inertial Fusion-Fission Energy) engine as a means of completely burning WG Pu and HEU. By combining a neutron-rich inertial fusion point source with energy-rich fission, the once-through closed fuel-cycle LIFE concept has the following characteristics: it is capable of efficiently burning excess weapons or separated civilian plutonium and highly enriched uranium; the fission blanket is sub-critical at all times (keff < 0.95); because LIFE can operate well beyond the point at which light water reactors (LWRs) need to be refueled due to burn-up of fissile material and the resulting drop in system reactivity, fuel burn-up of 99% or more appears feasible. The objective of this work is to develop LIFE technology for burning of WG-Pu and HEU.« less

University of Rochester, Laboratory for Laser Energetics

NASA Astrophysics Data System (ADS)

1987-01-01

In FY86 the Laboratory has produced a list of accomplishments in which it takes pride. LLE has met every laser-fusion program milestone to date in a program of research for direct-drive ultraviolet laser fusion originally formulated in 1981. LLE scientists authored or co-authored 135 scientific papers during 1985 to 1986. The collaborative experiments with NRL, LANL, and LLNL have led to a number of important ICF results. The cryogenic target system developed by KMS Fusion for LLE will be used in future high-density experiments on OMEGA to demonstrate the compression of thermonuclear fuel to 100 to 200 times that of solid (20 to 40 g/cm) in a test of the direct-drive concept, as noted in the National Academy of Sciences' report. The excellence of the advanced technology efforts at LLE is illustrated by the establishment of the Ultrafast Science Center by the Department of Defense through the Air Force Office of Scientific Research. Research in the Center will concentrate on bridging the gap between high-speed electronics and ultrafast optics by providing education, research, and development in areas critical to future communications and high-speed computer systems. The Laboratory for Laser Energetics continues its pioneering work on the interaction of intense radiation with matter. This includes inertial-fusion and advanced optical and optical electronics research; training people in the technology and applications of high-power, short-pulse lasers; and interacting with the scientific community, business, industry, and government to promote the growth of laser technology.

Effect of keyhole characteristics on porosity formation during pulsed laser-GTA hybrid welding of AZ31B magnesium alloy

NASA Astrophysics Data System (ADS)

Chen, Minghua; Xu, Jiannan; Xin, Lijun; Zhao, Zuofu; Wu, Fufa; Ma, Shengnan; Zhang, Yue

2017-06-01

This paper experimentally investigates the relationship between laser keyhole characteristics on the porosity formation during pulsed laser-GTA welding of magnesium alloy. Based on direct observations during welding process, the influences of laser keyhole state on the porosity formation were studied. Results show that the porosities in the joint are always at the bottom of fusion zone of the joint, which is closely related to the keyhole behavior. A large depth to wide ratio always leads to the increase of porosity generation chance. Keeping the keyhole outlet open for a longer time benefits the porosity restriction. Overlap of adjacent laser keyhole can effectively decrease the porosity generation, due to the cutting effect between adjacent laser keyholes. There are threshold overlap rate values for laser keyholes in different state.

Plasma-wall interaction in laser inertial fusion reactors: novel proposals for radiation tests of first wall materials

NASA Astrophysics Data System (ADS)

Alvarez Ruiz, J.; Rivera, A.; Mima, K.; Garoz, D.; Gonzalez-Arrabal, R.; Gordillo, N.; Fuchs, J.; Tanaka, K.; Fernández, I.; Briones, F.; Perlado, J.

2012-12-01

Dry-wall laser inertial fusion (LIF) chambers will have to withstand strong bursts of fast charged particles which will deposit tens of kJ m-2 and implant more than 1018 particles m-2 in a few microseconds at a repetition rate of some Hz. Large chamber dimensions and resistant plasma-facing materials must be combined to guarantee the chamber performance as long as possible under the expected threats: heating, fatigue, cracking, formation of defects, retention of light species, swelling and erosion. Current and novel radiation resistant materials for the first wall need to be validated under realistic conditions. However, at present there is a lack of facilities which can reproduce such ion environments. This contribution proposes the use of ultra-intense lasers and high-intense pulsed ion beams (HIPIB) to recreate the plasma conditions in LIF reactors. By target normal sheath acceleration, ultra-intense lasers can generate very short and energetic ion pulses with a spectral distribution similar to that of the inertial fusion ion bursts, suitable to validate fusion materials and to investigate the barely known propagation of those bursts through background plasmas/gases present in the reactor chamber. HIPIB technologies, initially developed for inertial fusion driver systems, provide huge intensity pulses which meet the irradiation conditions expected in the first wall of LIF chambers and thus can be used for the validation of materials too.

Laser Fusion of Mouse Embryonic Cells and Intra-Embryonic Fusion of Blastomeres without Affecting the Embryo Integrity

PubMed Central

Krivokharchenko, Alexander; Karmenyan, Artashes; Sarkisov, Oleg; Bader, Michael; Chiou, Arthur; Shakhbazyan, Avetik

2012-01-01

Manipulation with early mammalian embryos is the one of the most important approach to study preimplantation development. Artificial cell fusion is a research tool for various biotechnological experiments. However, the existing methods have various disadvantages, first of them impossibility to fuse selected cells within multicellular structures like mammalian preimplantation embryos. In our experiments we have successfully used high repetition rate picosecond near infrared laser beam for fusion of pairs of oocytes and oocytes with blastomeres. Fused cells looked morphologically normal and keep their ability for further divisions in vitro. We also fused two or three blastomeres inside four-cell mouse embryos. The presence of one, two or three nuclei in different blastomeres of the same early preimplantation mouse embryo was confirmed under UV-light after staining of DNA with the vital dye Hoechst-33342. The most of established embryos demonstrated high viability and developed in vitro to the blastocyst stage. We demonstrated for the first time the use of laser beam for the fusion of various embryonic cells of different size and of two or three blastomeres inside of four-cell mouse embryos without affecting the embryo’s integrity and viability. These embryos with blastomeres of various ploidy maybe unique model for numerous purposes. Thus, we propose laser optical manipulation as a new tool for investigation of fundamental mechanisms of mammalian development. PMID:23227157

Laser fusion of mouse embryonic cells and intra-embryonic fusion of blastomeres without affecting the embryo integrity.

PubMed

Krivokharchenko, Alexander; Karmenyan, Artashes; Sarkisov, Oleg; Bader, Michael; Chiou, Arthur; Shakhbazyan, Avetik

2012-01-01

Manipulation with early mammalian embryos is the one of the most important approach to study preimplantation development. Artificial cell fusion is a research tool for various biotechnological experiments. However, the existing methods have various disadvantages, first of them impossibility to fuse selected cells within multicellular structures like mammalian preimplantation embryos. In our experiments we have successfully used high repetition rate picosecond near infrared laser beam for fusion of pairs of oocytes and oocytes with blastomeres. Fused cells looked morphologically normal and keep their ability for further divisions in vitro. We also fused two or three blastomeres inside four-cell mouse embryos. The presence of one, two or three nuclei in different blastomeres of the same early preimplantation mouse embryo was confirmed under UV-light after staining of DNA with the vital dye Hoechst-33342. The most of established embryos demonstrated high viability and developed in vitro to the blastocyst stage. We demonstrated for the first time the use of laser beam for the fusion of various embryonic cells of different size and of two or three blastomeres inside of four-cell mouse embryos without affecting the embryo's integrity and viability. These embryos with blastomeres of various ploidy maybe unique model for numerous purposes. Thus, we propose laser optical manipulation as a new tool for investigation of fundamental mechanisms of mammalian development.

Influence of gas-powder laser cladding’s technological parameters on structural characteristics of corrosion-resistant steels’ restored surface layer

NASA Astrophysics Data System (ADS)

Krylova, S. E.; Oplesnin, S. P.; Goltyapin, M. I.

2018-03-01

The results of the developed industrial technology for surface restoration of corrosion-resistant steels by laser surfacing are presented in the article. A comparative analysis of the microstructure of the welded wear-resistant layer, the fusion zone with the base material and the diffusion zone for different technological surfacing regimes are given. Dyrometric studies and nondestructive testing of the deposited layer for defects were performed

Avalanche proton-boron fusion based on elastic nuclear collisions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eliezer, Shalom; Martinez Val, Josè Maria; Hora, Heinrich

2016-05-15

Recent experiments done at Prague with the 600 J/0.2 ns PALS laser interacting with a layer of boron dopants in a hydrogen enriched target have produced around 10{sup 9} alphas. We suggest that these unexpected very high fusion reactions of proton with {sup 11}B indicate an avalanche multiplication for the measured anomalously high nuclear reaction yields. This can be explained by elastic nuclear collisions in the broad 600 keV energy band, which is coincident with the high nuclear p-{sup 11}B fusion cross section, by the way of multiplication through generation of three secondary alpha particles from a single primarily produced alpha particle.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hora, H.; Korn, G.; Eliezer, S.

Measured highly elevated gains of proton–boron (HB11) fusion (Picciottoet al., Phys. Rev. X4, 031030 (2014)) confirmed the exceptional avalanche reaction process (Lalousiset al., Laser Part. Beams 32, 409 (2014); Horaet al., Laser Part. Beams33, 607 (2015)) for the combination of the non-thermal block ignition using ultrahigh intensity laser pulses of picoseconds duration. The ultrahigh accelerationabovemore » $$10^{20}~\\text{cm}~\\text{s}^{-2}$$ for plasma blocks was theoretically and numerically predicted since 1978 (Hora,Physics of Laser Driven Plasmas(Wiley, 1981), pp. 178 and 179) and measured (Sauerbrey, Phys. Plasmas3, 4712 (1996)) in exact agreement (Horaet al., Phys. Plasmas14, 072701 (2007)) when the dominating force was overcoming thermal processes. This is based on Maxwell’s stress tensor by the dielectric properties of plasma leading to the nonlinear (ponderomotive) force $$f_{\\text{NL}}$$ resulting in ultra-fast expanding plasma blocks by a dielectric explosion. Combining this with measured ultrahigh magnetic fields and the avalanche process opens an option for an environmentally absolute clean and economic boron fusion power reactor. Finally, this is supported also by other experiments with very high HB11 reactions under different conditions (Labauneet al., Nature Commun.4, 2506 (2013)).« less

Reconstruction of Axial Energy Deposition in Magnetic Liner Inertial Fusion Based on PECOS Shadowgraph Unfolds Using the AMR Code FLASH

NASA Astrophysics Data System (ADS)

Adams, Marissa; Jennings, Christopher; Slutz, Stephen; Peterson, Kyle; Gourdain, Pierre; U. Rochester-Sandia Collaboration

2017-10-01

Magnetic Liner Inertial Fusion (MagLIF) experiments incorporate a laser to preheat a deuterium filled capsule before compression via a magnetically imploding liner. In this work, we focus on the blast wave formed in the fuel during the laser preheat component of MagLIF, where approximately 1kJ of energy is deposited in 3ns into the capsule axially before implosion. To model blast waves directly relevant to experiments such as MagLIF, we inferred deposited energy from shadowgraphy of laser-only experiments preformed at the PECOS target chamber using the Z-Beamlet laser. These energy profiles were used to initialize 2-dimensional simulations using by the adaptive mesh refinement code FLASH. Gradients or asymmetries in the energy deposition may seed instabilities that alter the fuel's distribution, or promote mix, as the blast wave interacts with the liner wall. The AMR capabilities of FLASH allow us to study the development and dynamics of these instabilities within the fuel and their effect on the liner before implosion. Sandia Natl Labs is managed by NTES of Sandia, LLC., a subsidiary of Honeywell International, Inc, for the U.S. DOEs NNSA under contract DE-NA0003525.

Neutron residual stress measurement and numerical modeling in a curved thin-walled structure by laser powder bed fusion additive manufacturing

DOE PAGES

An, Ke; Yuan, Lang; Dial, Laura; ...

2017-09-11

Severe residual stresses in metal parts made by laser powder bed fusion additive manufacturing processes (LPBFAM) can cause both distortion and cracking during the fabrication processes. Limited data is currently available for both iterating through process conditions and design, and in particular, for validating numerical models to accelerate process certification. In this work, residual stresses of a curved thin-walled structure, made of Ni-based superalloy Inconel 625™ and fabricated by LPBFAM, were resolved by neutron diffraction without measuring the stress-free lattices along both the build and the transverse directions. The stresses of the entire part during fabrication and after cooling downmore » were predicted by a simplified layer-by-layer finite element based numerical model. The simulated and measured stresses were found in good quantitative agreement. The validated simplified simulation methodology will allow to assess residual stresses in more complex structures and to significantly reduce manufacturing cycle time.« less

Integrated fringe projection 3D scanning system for large-scale metrology based on laser tracker

NASA Astrophysics Data System (ADS)

Du, Hui; Chen, Xiaobo; Zhou, Dan; Guo, Gen; Xi, Juntong

2017-10-01

Large scale components exist widely in advance manufacturing industry,3D profilometry plays a pivotal role for the quality control. This paper proposes a flexible, robust large-scale 3D scanning system by integrating a robot with a binocular structured light scanner and a laser tracker. The measurement principle and system construction of the integrated system are introduced. And a mathematical model is established for the global data fusion. Subsequently, a flexible and robust method and mechanism is introduced for the establishment of the end coordination system. Based on this method, a virtual robot noumenon is constructed for hand-eye calibration. And then the transformation matrix between end coordination system and world coordination system is solved. Validation experiment is implemented for verifying the proposed algorithms. Firstly, hand-eye transformation matrix is solved. Then a car body rear is measured for 16 times for the global data fusion algorithm verification. And the 3D shape of the rear is reconstructed successfully.

Neutron residual stress measurement and numerical modeling in a curved thin-walled structure by laser powder bed fusion additive manufacturing

DOE Office of Scientific and Technical Information (OSTI.GOV)

An, Ke; Yuan, Lang; Dial, Laura

Severe residual stresses in metal parts made by laser powder bed fusion additive manufacturing processes (LPBFAM) can cause both distortion and cracking during the fabrication processes. Limited data is currently available for both iterating through process conditions and design, and in particular, for validating numerical models to accelerate process certification. In this work, residual stresses of a curved thin-walled structure, made of Ni-based superalloy Inconel 625™ and fabricated by LPBFAM, were resolved by neutron diffraction without measuring the stress-free lattices along both the build and the transverse directions. The stresses of the entire part during fabrication and after cooling downmore » were predicted by a simplified layer-by-layer finite element based numerical model. The simulated and measured stresses were found in good quantitative agreement. The validated simplified simulation methodology will allow to assess residual stresses in more complex structures and to significantly reduce manufacturing cycle time.« less

Improved pulse laser ranging algorithm based on high speed sampling

NASA Astrophysics Data System (ADS)

Gao, Xuan-yi; Qian, Rui-hai; Zhang, Yan-mei; Li, Huan; Guo, Hai-chao; He, Shi-jie; Guo, Xiao-kang

2016-10-01

Narrow pulse laser ranging achieves long-range target detection using laser pulse with low divergent beams. Pulse laser ranging is widely used in military, industrial, civil, engineering and transportation field. In this paper, an improved narrow pulse laser ranging algorithm is studied based on the high speed sampling. Firstly, theoretical simulation models have been built and analyzed including the laser emission and pulse laser ranging algorithm. An improved pulse ranging algorithm is developed. This new algorithm combines the matched filter algorithm and the constant fraction discrimination (CFD) algorithm. After the algorithm simulation, a laser ranging hardware system is set up to implement the improved algorithm. The laser ranging hardware system includes a laser diode, a laser detector and a high sample rate data logging circuit. Subsequently, using Verilog HDL language, the improved algorithm is implemented in the FPGA chip based on fusion of the matched filter algorithm and the CFD algorithm. Finally, the laser ranging experiment is carried out to test the improved algorithm ranging performance comparing to the matched filter algorithm and the CFD algorithm using the laser ranging hardware system. The test analysis result demonstrates that the laser ranging hardware system realized the high speed processing and high speed sampling data transmission. The algorithm analysis result presents that the improved algorithm achieves 0.3m distance ranging precision. The improved algorithm analysis result meets the expected effect, which is consistent with the theoretical simulation.

Description of the NIF Laser

DOE PAGES

Spaeth, M. L.; Manes, K. R.; Kalantar, D. H.; ...

2017-03-23

The possibility of imploding small capsules to produce mini-fusion explosions was explored soon after the first thermonuclear explosions in the early 1950s. Various technologies have been pursued to achieve the focused power and energy required for laboratory-scale fusion. Each technology has its own challenges. For example, electron and ion beams can deliver the large amounts of energy but must contend with Coulomb repulsion forces that make focusing these beams a daunting challenge. The demonstration of the first laser in 1960 provided a new option. Energy from laser beams can be focused and deposited within a small volume; the challenge becamemore » whether a practical laser system can be constructed that delivers the power and energy required while meeting all other demands for achieving a high-density, symmetric implosion. The National Ignition Facility (NIF) is the laser designed and built to meet the challenges for study of high-energy-density physics and inertial confinement fusion (ICF) implosions. This study describes the architecture, systems, and subsystems of NIF. Finally, it describes how they partner with each other to meet these new, complex demands and describes how laser science and technology were woven together to bring NIF into reality.« less

Disassembly time of deuterium-cluster-fusion plasma irradiated by an intense laser pulse.

PubMed

Bang, W

2015-07-01

Energetic deuterium ions from large deuterium clusters (>10nm diameter) irradiated by an intense laser pulse (>10(16)W/cm(2)) produce DD fusion neutrons for a time interval determined by the geometry of the resulting fusion plasma. We present an analytical solution of this time interval, the plasma disassembly time, for deuterium plasmas that are cylindrical in shape. Assuming a symmetrically expanding deuterium plasma, we calculate the expected fusion neutron yield and compare with an independent calculation of the yield using the concept of a finite confinement time at a fixed plasma density. The calculated neutron yields agree quantitatively with the available experimental data. Our one-dimensional simulations indicate that one could expect a tenfold increase in total neutron yield by magnetically confining a 10-keV deuterium fusion plasma for 10ns.

LIFE: a sustainable solution for developing safe, clean fusion power.

PubMed

Reyes, Susana; Dunne, Mike; Kramer, Kevin; Anklam, Tom; Havstad, Mark; Mazuecos, Antonio Lafuente; Miles, Robin; Martinez-Frias, Joel; Deri, Bob

2013-06-01

The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL) in California is currently in operation with the goal to demonstrate fusion energy gain for the first time in the laboratory-also referred to as "ignition." Based on these demonstration experiments, the Laser Inertial Fusion Energy (LIFE) power plant is being designed at LLNL in partnership with other institutions with the goal to deliver baseload electricity from safe, secure, sustainable fusion power in a time scale that is consistent with the energy market needs. For this purpose, the LIFE design takes advantage of recent advances in diode-pumped, solid-state laser technology and adopts the paradigm of Line Replaceable Units used on the NIF to provide high levels of availability and maintainability and mitigate the need for advanced materials development. The LIFE market entry plant will demonstrate the feasibility of a closed fusion fuel cycle, including tritium breeding, extraction, processing, refueling, accountability, and safety, in a steady-state power-producing device. While many fusion plant designs require large quantities of tritium for startup and operations, a range of design choices made for the LIFE fuel cycle act to reduce the in-process tritium inventory. This paper presents an overview of the delivery plan and the preconceptual design of the LIFE facility with emphasis on the key safety design principles being adopted. In order to illustrate the favorable safety characteristics of the LIFE design, some initial accident analysis results are presented that indicate potential for a more attractive licensing regime than that of current fission reactors.

Mechanical Behavior of Additively Manufactured Uranium-6 wt. pct. Niobium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, A. S.; Wraith, M. W.; Burke, S. C.

This report describes an effort to process uranium-6 weight% niobium using laser powder bed fusion. The chemistry, crystallography, microstructure and mechanical response resulting from this process are discussed with particular emphasis on the effect of the laser powder bed fusion process on impurities. In an effort to achieve homogenization and uniform mechanical behavior from different builds, as well as to induce a more conventional loading response, we explore post-processing heat treatments on this complex alloy. Elevated temperature heat treatment for recrystallization is evaluated and the effect of recrystallization on mechanical behavior in laser powder bed fusion processed U-6Nb is discussed.more » Wrought-like mechanical behavior and grain sizes are achieved through post-processing and are reported herein.« less

High-power fused assemblies enabled by advances in fiber-processing technologies

NASA Astrophysics Data System (ADS)

Wiley, Robert; Clark, Brett

2011-02-01

The power handling capabilities of fiber lasers are limited by the technologies available to fabricate and assemble the key optical system components. Previous tools for the assembly, tapering, and fusion of fiber laser elements have had drawbacks with regard to temperature range, alignment capability, assembly flexibility and surface contamination. To provide expanded capabilities for fiber laser assembly, a wide-area electrical plasma heat source was used in conjunction with an optimized image analysis method and a flexible alignment system, integrated according to mechatronic principles. High-resolution imaging and vision-based measurement provided feedback to adjust assembly, fusion, and tapering process parameters. The system was used to perform assembly steps including dissimilar-fiber splicing, tapering, bundling, capillary bundling, and fusion of fibers to bulk optic devices up to several mm in diameter. A wide range of fiber types and diameters were tested, including extremely large diameters and photonic crystal fibers. The assemblies were evaluated for conformation to optical and mechanical design criteria, such as taper geometry and splice loss. The completed assemblies met the performance targets and exhibited reduced surface contamination compared to assemblies prepared on previously existing equipment. The imaging system and image analysis algorithms provided in situ fiber geometry measurement data that agreed well with external measurement. The ability to adjust operating parameters dynamically based on imaging was shown to provide substantial performance benefits, particularly in the tapering of fibers and bundles. The integrated design approach was shown to provide sufficient flexibility to perform all required operations with a minimum of reconfiguration.

Seeding magnetic fields for laser-driven flux compression in high-energy-density plasmas.

PubMed

Gotchev, O V; Knauer, J P; Chang, P Y; Jang, N W; Shoup, M J; Meyerhofer, D D; Betti, R

2009-04-01

A compact, self-contained magnetic-seed-field generator (5 to 16 T) is the enabling technology for a novel laser-driven flux-compression scheme in laser-driven targets. A magnetized target is directly irradiated by a kilojoule or megajoule laser to compress the preseeded magnetic field to thousands of teslas. A fast (300 ns), 80 kA current pulse delivered by a portable pulsed-power system is discharged into a low-mass coil that surrounds the laser target. A >15 T target field has been demonstrated using a <100 J capacitor bank, a laser-triggered switch, and a low-impedance (<1 Omega) strip line. The device has been integrated into a series of magnetic-flux-compression experiments on the 60 beam, 30 kJ OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. The initial application is a novel magneto-inertial fusion approach [O. V. Gotchev et al., J. Fusion Energy 27, 25 (2008)] to inertial confinement fusion (ICF), where the amplified magnetic field can inhibit thermal conduction losses from the hot spot of a compressed target. This can lead to the ignition of massive shells imploded with low velocity-a way of reaching higher gains than is possible with conventional ICF.

Hot and dense plasma probing by soft X-ray lasers

NASA Astrophysics Data System (ADS)

Krůs, M.; Kozlová, M.; Nejdl, J.; Rus, B.

2018-01-01

Soft X-ray lasers, due to their short wavelength, its brightness, and good spatial coherence, are excellent sources for the diagnostics of dense plasmas (up to 1025 cm-3) which are relevant to e.g. inertial fusion. Several techniques and experimental results, which are obtained at the quasi-steady state scheme being collisionally pumped 21.2 nm neon-like zinc laser installed at PALS Research Center, are presented here; among them the plasma density measurement by a double Lloyd mirror interferometer, deflectometer based on Talbot effect measuring plasma density gradients itself, with a following ray tracing postprocessing. Moreover, the high spatial resolution (nm scale) plasma images can be obtained when soft X-ray lasers are used.

Visualization of the influence of the air conditioning system to the high-power laser beam quality with the modulation coherent imaging method.

PubMed

Tao, Hua; Veetil, Suhas P; Pan, Xingchen; Liu, Cheng; Zhu, Jianqiang

2015-08-01

Air conditioning systems can lead to dynamic phase change in the laser beams of high-power laser facilities for the inertial confinement fusion, and this kind of phase change cannot be measured by most of the commonly employed Hartmann wavefront sensor or interferometry due to some uncontrollable factors, such as too large laser beam diameters and the limited space of the facility. It is demonstrated that this problem can be solved using a scheme based on modulation coherent imaging, and thus the influence of the air conditioning system on the performance of the high-power facility can be evaluated directly.

Development of large-aperture electro-optical switch for high power laser at CAEP

NASA Astrophysics Data System (ADS)

Zhang, Xiongjun; Wu, Dengsheng; Zhang, Jun; Lin, Donghui; Zheng, Jiangang; Zheng, Kuixing

2015-02-01

Large-aperture electro-optical switch based on plasma Pockels cell (PPC) is one of important components for inertial confinement fusion (ICF) laser facility. We have demonstrated a single-pulse driven 4×1 PPC with 400mm×400mm aperture for SGIII laser facility. And four 2×1 PPCs modules with 350mm×350mm aperture have been operated in SGII update laser facility. It is different to the PPC of NIF and LMJ for its simple operation to perform Pockels effect. With optimized operation parameters, the PPCs meet the SGII-U laser requirement of four-pass amplification control. Only driven by one high voltage pulser, the simplified PPC system would be provided with less associated diagnostics, and higher reliability. To farther reduce the insert loss of the PPC, research on the large-aperture PPC based on DKDP crystal driven by one pulse is developed. And several single-pulse driven PPCs with 80mm×80mm DKDP crystal have been manufactured and operated in laser facilities.

Electron Shock Ignition of Inertial Fusion Targets

DOE PAGES

Shang, W. L.; Betti, R.; Hu, S. X.; ...

2017-11-07

Here, it is shown that inertial fusion targets designed with low implosion velocities can be shock ignited using laser–plasma interaction generated hot electrons (hot-e) to obtain high-energy gains. These designs are robust to multimode asymmetries and are predicted to ignite even for significantly distorted implosions. Electron shock ignition requires tens of kilojoules of hot-e, which can only be produced on a large laser facility like the National Ignition Facility, with the laser to hot-e conversion efficiency greater than 10% at laser intensities ~10 16 W/cm 2.

Monochromatic x-ray radiography of laser-driven spherical targets using high-energy, picoseconds LFEX laser

NASA Astrophysics Data System (ADS)

Sawada, Hiroshi; Fujioka, S.; Lee, S.; Arikawa, Y.; Shigemori, K.; Nagatomo, H.; Nishimura, H.; Sunahara, A.; Theobald, W.; Perez, F.; Patel, P. K.; Beg, F. N.

2015-11-01

Formation of a high density fusion fuel is essential in both conventional and advanced Inertial Confinement Fusion (ICF) schemes for the self-sustaining fusion process. In cone-guided Fast Ignition (FI), a metal cone is attached to a spherical target to maintain the path for the injection of an intense short-pulse ignition laser from blow-off plasma created when nanoseconds compression lasers drive the target. We have measured a temporal evolution of a compressed deuterated carbon (CD) sphere using 4.5 keV K-alpha radiography with the Kilo-Joule, picosecond LFEX laser at the Institute of Laser Engineering. A 200 μm CD sphere attached to the tip of a Au cone was directly driven by 9 Gekko XII beams with 300 J/beam in a 1.3 ns Gaussian pulse. The LFEX laser irradiated on a Ti foil to generate 4.51 Ti K-alpha x-ray. By varying the delay between the compression and backlighter lasers, the measured radiograph images show an increase of the areal density of the imploded target. The detail of the quantitative analyses to infer the areal density and comparisons to hydrodynamics simulations will be presented. This work was performed with the support and under the auspices of the NIFS Collaboration Research program (NIFS13KUGK072). H.S. was supported by the UNR's International Activities Grant program.

Laser or charged-particle-beam fusion reactor with direct electric generation by magnetic flux compression

DOEpatents

Lasche, G.P.

1983-09-29

The invention is a laser or particle-beam-driven fusion reactor system which takes maximum advantage of both the very short pulsed nature of the energy release of inertial confinement fusion (ICF) and the very small volumes within which the thermonuclear burn takes place. The pulsed nature of ICF permits dynamic direct energy conversion schemes such as magnetohydrodynamic (MHD) generation and magnetic flux compression; the small volumes permit very compact blanket geometries. By fully exploiting these characteristics of ICF, it is possible to design a fusion reactor with exceptionally high power density, high net electric efficiency, and low neutron-induced radioactivity. The invention includes a compact blanket design and method and apparatus for obtaining energy utilizing the compact blanket.

The National Ignition Facility: The Path to a Carbon-Free Energy Future

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stolz, C J

2011-03-16

The National Ignition Facility (NIF), the world's largest and most energetic laser system, is now operational at Lawrence Livermore National Laboratory (LLNL). The NIF will enable exploration of scientific problems in national strategic security, basic science and fusion energy. One of the early NIF goals centers on achieving laboratory-scale thermonuclear ignition and energy gain, demonstrating the feasibility of laser fusion as a viable source of clean, carbon-free energy. This talk will discuss the precision technology and engineering challenges of building the NIF and those we must overcome to make fusion energy a commercial reality.

The National Ignition Facility: the path to a carbon-free energy future.

PubMed

Stolz, Christopher J

2012-08-28

The National Ignition Facility (NIF), the world's largest and most energetic laser system, is now operational at Lawrence Livermore National Laboratory. The NIF will enable exploration of scientific problems in national strategic security, basic science and fusion energy. One of the early NIF goals centres on achieving laboratory-scale thermonuclear ignition and energy gain, demonstrating the feasibility of laser fusion as a viable source of clean, carbon-free energy. This talk will discuss the precision technology and engineering challenges of building the NIF and those we must overcome to make fusion energy a commercial reality.

Infrared laser thermal fusion of blood vessels: preliminary ex vivo tissue studies.

PubMed

Cilip, Christopher M; Rosenbury, Sarah B; Giglio, Nicholas; Hutchens, Thomas C; Schweinsberger, Gino R; Kerr, Duane; Latimer, Cassandra; Nau, William H; Fried, Nathaniel M

2013-05-01

Suture ligation of blood vessels during surgery can be time-consuming and skill-intensive. Energy-based, electrosurgical, and ultrasonic devices have recently replaced the use of sutures and mechanical clips (which leave foreign objects in the body) for many surgical procedures, providing rapid hemostasis during surgery. However, these devices have the potential to create an undesirably large collateral zone of thermal damage and tissue necrosis. We explore an alternative energy-based technology, infrared lasers, for rapid and precise thermal coagulation and fusion of the blood vessel walls. Seven near-infrared lasers (808, 980, 1075, 1470, 1550, 1850 to 1880, and 1908 nm) were tested during preliminary tissue studies. Studies were performed using fresh porcine renal vessels, ex vivo, with native diameters of 1 to 6 mm, and vessel walls flattened to a total thickness of 0.4 mm. A linear beam profile was applied normal to the vessel for narrow, full-width thermal coagulation. The laser irradiation time was 5 s. Vessel burst pressure measurements were used to determine seal strength. The 1470 nm laser wavelength demonstrated the capability of sealing a wide range of blood vessels from 1 to 6 mm diameter with burst strengths of 578 ± 154, 530 ± 171, and 426 ± 174  mmHg for small, medium, and large vessel diameters, respectively. Lateral thermal coagulation zones (including the seal) measured 1.0 ± 0.4  mm on vessels sealed at this wavelength. Other laser wavelengths (1550, 1850 to 1880, and 1908 nm) were also capable of sealing vessels, but were limited by lower vessel seal pressures, excessive charring, and/or limited power output preventing treatment of large vessels (>4  mm outer diameter).

Use Of Adaptive Optics Element For Wavefront Error Correction In The Gemini CO2 Laser Fusion System

NASA Astrophysics Data System (ADS)

Viswanathan, V. K.; Parker, J. V.; Nussmier, T. A.; Swigert, C. J.; King, W.; Lau, A. S.; Price, K.

1980-11-01

The Gemini two beam CO2 laser fusion system incorporates a complex optical system with nearly 100 surfaces per beam, associated with the generation, transport and focusing of CO2 laser beams for irradiating laser fusion targets. Even though the system is nominally diffraction limited, in practice the departure from the ideal situation drops the Strehl ratio to 0.24. This departure is caused mostly by the imperfections in the large (34 cm optical clear aperture diameter) state-of-the-art components like the sodium chloride windows and micromachined mirrors. While the smaller optical components also contribute to this degradation, the various possible misalignments and nonlinear effects are considered to contribute very little to it. Analysis indicates that removing the static or quasi-static errors can dramatically improve the Strehl ratio. A deformable mirror which can comfortably achieve the design goal Strehl ratio of >= 0.7 is described, along with the various system trade-offs in the design of the mirror and the control system.

Neutron Generation by Laser-Driven Spherically Convergent Plasma Fusion.

PubMed

Ren, G; Yan, J; Liu, J; Lan, K; Chen, Y H; Huo, W Y; Fan, Z; Zhang, X; Zheng, J; Chen, Z; Jiang, W; Chen, L; Tang, Q; Yuan, Z; Wang, F; Jiang, S; Ding, Y; Zhang, W; He, X T

2017-04-21

We investigate a new laser-driven spherically convergent plasma fusion scheme (SCPF) that can produce thermonuclear neutrons stably and efficiently. In the SCPF scheme, laser beams of nanosecond pulse duration and 10^{14}-10^{15}  W/cm^{2} intensity uniformly irradiate the fuel layer lined inside a spherical hohlraum. The fuel layer is ablated and heated to expand inwards. Eventually, the hot fuel plasmas converge, collide, merge, and stagnate at the central region, converting most of their kinetic energy to internal energy, forming a thermonuclear fusion fireball. With the assumptions of steady ablation and adiabatic expansion, we theoretically predict the neutron yield Y_{n} to be related to the laser energy E_{L}, the hohlraum radius R_{h}, and the pulse duration τ through a scaling law of Y_{n}∝(E_{L}/R_{h}^{1.2}τ^{0.2})^{2.5}. We have done experiments at the ShengGuangIII-prototype facility to demonstrate the principle of the SCPF scheme. Some important implications are discussed.

Neutron Generation by Laser-Driven Spherically Convergent Plasma Fusion

NASA Astrophysics Data System (ADS)

Ren, G.; Yan, J.; Liu, J.; Lan, K.; Chen, Y. H.; Huo, W. Y.; Fan, Z.; Zhang, X.; Zheng, J.; Chen, Z.; Jiang, W.; Chen, L.; Tang, Q.; Yuan, Z.; Wang, F.; Jiang, S.; Ding, Y.; Zhang, W.; He, X. T.

2017-04-01

We investigate a new laser-driven spherically convergent plasma fusion scheme (SCPF) that can produce thermonuclear neutrons stably and efficiently. In the SCPF scheme, laser beams of nanosecond pulse duration and 1 014- 1 015 W /cm2 intensity uniformly irradiate the fuel layer lined inside a spherical hohlraum. The fuel layer is ablated and heated to expand inwards. Eventually, the hot fuel plasmas converge, collide, merge, and stagnate at the central region, converting most of their kinetic energy to internal energy, forming a thermonuclear fusion fireball. With the assumptions of steady ablation and adiabatic expansion, we theoretically predict the neutron yield Yn to be related to the laser energy EL, the hohlraum radius Rh, and the pulse duration τ through a scaling law of Yn∝(EL/Rh1.2τ0.2 )2.5. We have done experiments at the ShengGuangIII-prototype facility to demonstrate the principle of the SCPF scheme. Some important implications are discussed.

Accelerating Into the Future: From 0 to GeV in a Few Centimeters (LBNL Summer Lecture Series)

ScienceCinema

Leemans, Wim [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Accelerator and Fusion Research Division (AFRD) and Laser Optics and Accelerator Systems Integrated Studies (LOASIS)

2018-05-04

Summer Lecture Series 2008: By exciting electric fields in plasma-based waveguides, lasers accelerate electrons in a fraction of the distance conventional accelerators require. The Accelerator and Fusion Research Division's LOASIS program, headed by Wim Leemans, has used 40-trillion-watt laser pulses to deliver billion-electron-volt (1 GeV) electron beams within centimeters. Leemans looks ahead to BELLA, 10-GeV accelerating modules that could power a future linear collider.

Accelerating Into the Future: From 0 to GeV in a Few Centimeters (LBNL Summer Lecture Series)

ScienceCinema

Leemans, Wim [LOASIS Program, AFRD

2017-12-09

July 8, 2008 Berkeley Lab lecture: By exciting electric fields in plasma-based waveguides, lasers accelerate electrons in a fraction of the distance conventional accelerators require. The Accelerator and Fusion Research Division's LOASIS program, headed by Wim Leemans, has used 40-trillion-watt laser pulses to deliver billion-electron-volt (1 GeV) electron beams within centimeters. Leemans looks ahead to BELLA, 10-GeV accelerating modules that could power a future linear collider.

EDITORIAL: Inertial Fusion State of the Art---A Collection of Overview and Technical Papers from IFSA2003

NASA Astrophysics Data System (ADS)

Hogan, W. J.

2004-12-01

The Third International Conference on Inertial Fusion Sciences and Applications (IFSA2003) was held in Monterey, CA, USA, on 7--12 September 2003. The goal of IFSA2003 was to bring together scientists and engineers in the fields of inertial fusion sciences, high energy density physics, inertial fusion energy (IFE) and other related research and applications. By all measures IFSA2003 was a resounding success. IFSA2003 was hosted by the University of California, which was supported in organizing the conference by seven institutions: General Atomics, Lawrence Berkeley National Laboratory, Lawrence Livermore National Laboratory, Los Alamos National Laboratory, Naval Research Laboratory, Sandia National Laboratory and the University of Rochester, Laboratory for Laser Energetics. IFSA2003 was the largest IFSA conference yet with 405 participants from 17 countries. Approximately 430 papers were presented and 236 appeared in the Proceedings, published in July 2004 by the American Nuclear Society [1]. A subset of the Nuclear Fusion Board of Editors, those who work on inertial confinement fusion (ICF), recommended creating this special issue of Nuclear Fusion by selecting a representative cross-section of the papers presented at IFSA2003. Authors of the selected papers were asked to expand their papers and make them suitable for publication in it Nuclear Fusion. Nineteen papers are presented in this special issue. They represent a cross-section of the papers presented at IFSA2003. However, there was no attempt to represent the `feel' of the conference by having the same fraction of papers on each topic as existed at IFSA. There were far more detailed scientific papers at IFSA than are presented in this special issue. However, in the interest of giving the reader a cross-section of the papers and showing the entire breadth of ICF research going on, we have biased the selection process toward review papers. The first three papers here are based upon the keynote talks at IFSA2003 and are, therefore, overviews of all ICF research being done in the Americas, Asia, and Europe. The next two papers are also reviews but of a different sort. The Teller Medal is awarded at the IFSA conferences for pioneering work and leadership in inertial fusion and high energy density science. The two recipients for 2003 were H. Takabe of the Institute of Laser Engineering at Osaka University and L. Suter of Lawrence Livermore National Laboratory. These awardees were asked to deliver the two Teller Lectures at IFSA based upon the work for which they were being honoured. The papers presented here are expansions of those two review talks. Suter chose to focus his review on his recent work on ignition physics for targets driven by 0.54 m light. This is of interest because large facilities like the National Ignition Facility (NIF) will deliver much more energy in the frequency doubled wavelength than in the frequency tripled one. Takabe, on the other hand chose to give a historical perspective of his lifelong work. The other 14 papers were selected to represent a cross-section of the research being conducted in the science and engineering of inertial fusion. The papers by Haan et al and Holstein et al represent some of the recent progress in target design calculations for the ignition first experiments. Haan presents his team's work on indirect drive ignition targets (driven by 0.35 m) intended for the National Ignition Facility (NIF) when all the beamlines are activated. Holstein does the same for targets being design for the Laser MegaJoule (LMJ). Suter's paper, presented earlier as a Teller Lecture also falls into this ignition target physics category. The next four papers look at some of the exciting high energy density physics being studied in ICF facilities around the world. Glenzer et al looks at stimulated light scattering processes in hot dense plasmas. Pukhov et al look at relativistic laser-plasma interactions that produce energetic particles and x-rays. Peyrusse et al examine atomic physics and radiative processes in hot dense plasmas. Koenig et al examine ways to simulate planetary physics processes using high pressures generated in laser driven shocks. Non-laser approaches to inertial fusion were also fully represented at IFSA2003. The paper by Lebedev et al shows important physics developments in Z-pinch plasmas. Sharp et al present chamber transport modelling for heavy ion fusion drivers. Technology development studies were also well represented at IFSA2003. There was a special session on facility and driver developments that contained several papers. Presented here are the papers by Miller et al on the NIF, Danson et al on the Vulcan petawatt facility, and Myers et al on KrF lasers for IFE. A paper by Goodin et al shows progress in finding cost effective target manufacturing methods for IFE. Finally, there were many papers at IFSA2003 that focused upon the very promising but more immature field of fast ignition. Barty et al give an overview of the development issues for short pulse lasers that will be essential if fast ignition is to become mainstream. A paper by Kodama et al looks at target physics using cone focus targets. Fast ignition lasers and innovative target physics within this concept were a `hot topic' at IFSA2003. The IFSA conferences have become the principal forum for the exchange of research results in inertial fusion and high energy and density science. There is a unique blend of science and technology. All fields of inertial fusion are represented. This special issue is a snapshot and a cross-section of the field at this time. We hope the reader is encouraged to look into more of the papers in areas that interest them. References [1] Inertial Fusion Sciences and Applications: State of the Art 2003 ed B. Hammel, D. Meyerhofer, J. Meyer-ter-Vehn and H. Azechi American Nuclear Society (July 2004) These IFSA2003 proceedings may be purchased on-line at http://www.ans.org.

Refractive Index Seen by a Probe Beam Interacting with a Laser-Plasma System

NASA Astrophysics Data System (ADS)

Turnbull, D.; Goyon, C.; Kemp, G. E.; Pollock, B. B.; Mariscal, D.; Divol, L.; Ross, J. S.; Patankar, S.; Moody, J. D.; Michel, P.

2017-01-01

We report the first complete set of measurements of a laser-plasma optical system's refractive index, as seen by a second probe laser beam, as a function of the relative wavelength shift between the two laser beams. Both the imaginary and real refractive index components are found to be in good agreement with linear theory using plasma parameters measured by optical Thomson scattering and interferometry; the former is in contrast to previous work and has implications for crossed-beam energy transfer in indirect-drive inertial confinement fusion, and the latter is measured for the first time. The data include the first demonstration of a laser-plasma polarizer with 85 %- 87 % extinction for the particular laser and plasma parameters used in this experiment, complementing the existing suite of high-power, tunable, and ultrafast plasma-based photonic devices.

Refractive Index Seen by a Probe Beam Interacting with a Laser-Plasma System.

PubMed

Turnbull, D; Goyon, C; Kemp, G E; Pollock, B B; Mariscal, D; Divol, L; Ross, J S; Patankar, S; Moody, J D; Michel, P

2017-01-06

We report the first complete set of measurements of a laser-plasma optical system's refractive index, as seen by a second probe laser beam, as a function of the relative wavelength shift between the two laser beams. Both the imaginary and real refractive index components are found to be in good agreement with linear theory using plasma parameters measured by optical Thomson scattering and interferometry; the former is in contrast to previous work and has implications for crossed-beam energy transfer in indirect-drive inertial confinement fusion, and the latter is measured for the first time. The data include the first demonstration of a laser-plasma polarizer with 85%-87% extinction for the particular laser and plasma parameters used in this experiment, complementing the existing suite of high-power, tunable, and ultrafast plasma-based photonic devices.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holmlid, Leif, E-mail: holmlid@chem.gu.se

Previous results from laser-induced processes in ultra-dense deuterium D(0) give conclusive evidence for ejection of neutral massive particles with energy >10 MeV u{sup −1}. Such particles can only be formed from nuclear processes like nuclear fusion at the low laser intensity used. Heat generation is of interest for future fusion energy applications and has now been measured by a small copper (Cu) cylinder surrounding the laser target. The temperature rise of the Cu cylinder is measured with an NTC resistor during around 5000 laser shots per measured point. No heating in the apparatus or the gas feed is normally used.more » The fusion process is suboptimal relative to previously published studies by a factor of around 10. The small neutral particles H{sub N}(0) of ultra-dense hydrogen (size of a few pm) escape with a substantial fraction of the energy. Heat loss to the D{sub 2} gas (at <1 mbar pressure) is measured and compensated for under various conditions. Heat release of a few W is observed, at up to 50% higher energy than the total laser input thus a gain of 1.5. This is uniquely high for the use of deuterium as fusion fuel. With a slightly different setup, a thermal gain of 2 is reached, thus clearly above break-even for all neutronicity values possible. Also including the large kinetic energy which is directly measured for MeV particles leaving through a small opening gives a gain of 2.3. Taking into account the lower efficiency now due to the suboptimal fusion process, previous studies indicate a gain of at least 20 during long periods.« less

Laser-induced tissue fluorescence in radiofrequency tissue-fusion characterization.

PubMed

Su, Lei; Fonseca, Martina B; Arya, Shobhit; Kudo, Hiromi; Goldin, Robert; Hanna, George B; Elson, Daniel S

2014-01-01

Heat-induced tissue fusion is an important procedure in modern surgery and can greatly reduce trauma, complications, and mortality during minimally invasive surgical blood vessel anastomosis, but it may also have further benefits if applied to other tissue types such as small and large intestine anastomoses. We present a tissue-fusion characterization technology using laser-induced fluorescence spectroscopy, which provides further insight into tissue constituent variations at the molecular level. In particular, an increase of fluorescence intensity in 450- to 550-nm range for 375- and 405-nm excitation suggests that the collagen cross-linking in fused tissues increased. Our experimental and statistical analyses showed that, by using fluorescence spectral data, good fusion could be differentiated from other cases with an accuracy of more than 95%. This suggests that the fluorescence spectroscopy could be potentially used as a feedback control method in online tissue-fusion monitoring.

Disassembly time of deuterium-cluster-fusion plasma irradiated by an intense laser pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bang, W.

Energetic deuterium ions from large deuterium clusters (>10 nm diameter) irradiated by an intense laser pulse (>10¹⁶ W/cm²) produce DD fusion neutrons for a time interval determined by the geometry of the resulting fusion plasma. We show an analytical solution of this time interval, the plasma disassembly time, for deuterium plasmas that are cylindrical in shape. Assuming a symmetrically expanding deuterium plasma, we calculate the expected fusion neutron yield and compare with an independent calculation of the yield using the concept of a finite confinement time at a fixed plasma density. The calculated neutron yields agree quantitatively with the availablemore » experimental data. Our one-dimensional simulations indicate that one could expect a tenfold increase in total neutron yield by magnetically confining a 10 - keV deuterium fusion plasma for 10 ns.« less

Disassembly time of deuterium-cluster-fusion plasma irradiated by an intense laser pulse

DOE PAGES

Bang, W.

2015-07-02

Energetic deuterium ions from large deuterium clusters (>10 nm diameter) irradiated by an intense laser pulse (>10¹⁶ W/cm²) produce DD fusion neutrons for a time interval determined by the geometry of the resulting fusion plasma. We show an analytical solution of this time interval, the plasma disassembly time, for deuterium plasmas that are cylindrical in shape. Assuming a symmetrically expanding deuterium plasma, we calculate the expected fusion neutron yield and compare with an independent calculation of the yield using the concept of a finite confinement time at a fixed plasma density. The calculated neutron yields agree quantitatively with the availablemore » experimental data. Our one-dimensional simulations indicate that one could expect a tenfold increase in total neutron yield by magnetically confining a 10 - keV deuterium fusion plasma for 10 ns.« less

Interplay of Laser-Plasma Interactions and Inertial Fusion Hydrodynamics.

PubMed

Strozzi, D J; Bailey, D S; Michel, P; Divol, L; Sepke, S M; Kerbel, G D; Thomas, C A; Ralph, J E; Moody, J D; Schneider, M B

2017-01-13

The effects of laser-plasma interactions (LPI) on the dynamics of inertial confinement fusion hohlraums are investigated via a new approach that self-consistently couples reduced LPI models into radiation-hydrodynamics numerical codes. The interplay between hydrodynamics and LPI-specifically stimulated Raman scatter and crossed-beam energy transfer (CBET)-mostly occurs via momentum and energy deposition into Langmuir and ion acoustic waves. This spatially redistributes energy coupling to the target, which affects the background plasma conditions and thus, modifies laser propagation. This model shows reduced CBET and significant laser energy depletion by Langmuir waves, which reduce the discrepancy between modeling and data from hohlraum experiments on wall x-ray emission and capsule implosion shape.

Direct measurement of the impulse in a magnetic thrust chamber system for laser fusion rocket

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maeno, Akihiro; Yamamoto, Naoji; Nakashima, Hideki

2011-08-15

An experiment is conducted to measure an impulse for demonstrating a magnetic thrust chamber system for laser fusion rocket. The impulse is produced by the interaction between plasma and magnetic field. In the experiment, the system consists of plasma and neodymium permanent magnets. The plasma is created by a single-beam laser aiming at a polystyrene spherical target. The impulse is 1.5 to 2.2 {mu}Ns by means of a pendulum thrust stand, when the laser energy is 0.7 J. Without magnetic field, the measured impulse is found to be zero. These results indicate that the system for generating impulse is working.

Sub-Nanosecond Cinematography In Laser Fusion Research: Current Techniques And Applications At The Lawrence Livermore National Laboratory*

NASA Astrophysics Data System (ADS)

Coleman, Lamar W...

1985-02-01

Progress in laser fusion research has increased the need for detail and precision in the diagnosis of experiments. This has spawned the development and use of sophisticated sub-nanosecond resolution diavostic systems. These systems typically use ultrafast x-ray or optical streak caAleras in combination. with spatially imaging or spectrally dispersing elements. These instruments provide high resolution data essential for understanding the processes occurrilltg in the interaction. of high. intensity laser light with targets. Several of these types of instruments and their capabilities will be discussed. The utilization of these kinds of diagnostics systems on the nearly completed 100 kJ Nova laser facility will be described.

Sub-nanosecond cinematography in laser fusion research: Current techniques and applications at the Lawrence Livermore Laboratory

NASA Astrophysics Data System (ADS)

Coleman, L. W.

1985-01-01

Progress in laser fusion research has increased the need for detail and precision in the diagnosis of experiments. This has spawned the development and use of sophisticated sub-nanosecond resolution diagnostic systems. These systems typically use ultrafast X-ray or optical streak cameras in combination with spatially imaging or spectrally dispersing elements. These instruments provide high resolution data essential for understanding the processes occurring in the interaction of high intensity laser light with targets. Several of these types of instruments and their capabilities will be discussed. The utilization of these kinds of diagnostics systems on the nearly completed 100 kJ Nova laser facility will be described.

Effect of Heat Input and Post-Weld Heat Treatment on the Mechanical and Metallurgical Characteristics of Laser-Welded Maraging Steel Joints

NASA Astrophysics Data System (ADS)

Karthikeyan, R.; Saravanan, M.; Singaravel, B.; Sathiya, P.

This paper investigates the impact of heat input and post-weld aging behavior at different temperatures on the laser paper welded maraging steel grade 250. Three different levels of heat inputs were chosen and CO2 laser welding was performed. Aging was done at six different temperatures: 360∘C, 400∘C, 440∘C, 480∘C, 520∘C and 560∘C. The macrostructure and microstructure of the fusion zone were obtained using optical microscope. The microhardness test was performed on the weld zone. Tensile tests and impact tests were carried out for the weld samples and different age-treated weld samples. Fracture surfaces were investigated by scanning electron microscopy (SEM). Microhardness values of the fusion zone increased with increasing aging temperature, while the base metal microhardness value decreased. Tensile properties increased with aging temperature up to 480∘C and reduced for 520∘C and 560∘C. This was mainly due to the formation of reverted austenite beyond 500∘C. XRD analysis confirmed the formation of reverted austenite.

Investigation of defect rate of lap laser welding of stainless steel railway vehicles car body

NASA Astrophysics Data System (ADS)

Wang, Hongxiao

2015-02-01

In order to resolve the disadvantages such as poor appearance quality, poor tightness, low efficiency of resistance spot welding of stainless steel rail vehicles, partial penetration lap laser welding process was investigated widely. But due to the limitation of processing technology, there will be local incomplete fusion in the lap laser welding seam. Defect rate is the ratio of the local incomplete fusion length to the weld seam length. The tensile shear strength under different defect rate and its effect on the car body static strength are not clear. It is necessary to find the biggest defect rate by numerical analysis of effects of different defect rates on the laser welding stainless steel rail vehicle body structure strength ,and tests of laser welding shear tensile strength.

Phase Aberrations And Beam Cleanup Techniques In Carbon-Dioxide Laser Fusion Systems

NASA Astrophysics Data System (ADS)

Viswanathan, V. K.

1981-12-01

This paper describes the various carbon dioxide laser fusion systems at Los Alamos from the point of view of an optical designer. The types of phase aberrations present in these systems, as well as the beam cleanup techniques that can be used to improve the beam optical quality, are discussed. As this is a review article, some previously published results are also used where relevant.

Quasi-CW 110 kW AlGaAs Laser Diode Array Module for Inertial Fusion Energy Laser Driver

NASA Astrophysics Data System (ADS)

Kawashima, Toshiyuki; Kanzaki, Takeshi; Matsui, Ken; Kato, Yoshinori; Matsui, Hiroki; Kanabe, Tadashi; Yamanaka, Masanobu; Nakatsuka, Masahiro; Izawa, Yasukazu; Nakai, Sadao; Miyamoto, Masahiro; Kan, Hirofumi; Hiruma, Teruo

2001-12-01

We have successfully demonstrated a large aperture 803 nm AlGaAs diode laser module as a pump source for a 1053 nm, 10 J output Nd:glass slab laser amplifier for diode-pumped solid-state laser (DPSSL) fusion driver. Detailed performance results of the laser diode module are presented, including bar package and stack configuration, and their thermal design and analysis. A sufficiently low thermal impedance of the stack was realized by combining backplane liquid cooling configuration with modular bar package architecture. Total peak power of 110 kW and electrical to optical conversion efficiency of 46% were obtained from the module consisting of a total of 1000 laser diode bars. A peak intensity of 2.6 kW/cm2 was accomplished across an emitting area of 418 mm× 10 mm. Currently, this laser diode array module with a large two-dimensional aperture is, to our knowledge, the only operational pump source for the high output energy DPSSL.

Direct-drive inertial confinement fusion: A review

NASA Astrophysics Data System (ADS)

Craxton, R. S.; Anderson, K. S.; Boehly, T. R.; Goncharov, V. N.; Harding, D. R.; Knauer, J. P.; McCrory, R. L.; McKenty, P. W.; Meyerhofer, D. D.; Myatt, J. F.; Schmitt, A. J.; Sethian, J. D.; Short, R. W.; Skupsky, S.; Theobald, W.; Kruer, W. L.; Tanaka, K.; Betti, R.; Collins, T. J. B.; Delettrez, J. A.; Hu, S. X.; Marozas, J. A.; Maximov, A. V.; Michel, D. T.; Radha, P. B.; Regan, S. P.; Sangster, T. C.; Seka, W.; Solodov, A. A.; Soures, J. M.; Stoeckl, C.; Zuegel, J. D.

2015-11-01

The direct-drive, laser-based approach to inertial confinement fusion (ICF) is reviewed from its inception following the demonstration of the first laser to its implementation on the present generation of high-power lasers. The review focuses on the evolution of scientific understanding gained from target-physics experiments in many areas, identifying problems that were demonstrated and the solutions implemented. The review starts with the basic understanding of laser-plasma interactions that was obtained before the declassification of laser-induced compression in the early 1970s and continues with the compression experiments using infrared lasers in the late 1970s that produced thermonuclear neutrons. The problem of suprathermal electrons and the target preheat that they caused, associated with the infrared laser wavelength, led to lasers being built after 1980 to operate at shorter wavelengths, especially 0.35 μm—the third harmonic of the Nd:glass laser—and 0.248 μm (the KrF gas laser). The main physics areas relevant to direct drive are reviewed. The primary absorption mechanism at short wavelengths is classical inverse bremsstrahlung. Nonuniformities imprinted on the target by laser irradiation have been addressed by the development of a number of beam-smoothing techniques and imprint-mitigation strategies. The effects of hydrodynamic instabilities are mitigated by a combination of imprint reduction and target designs that minimize the instability growth rates. Several coronal plasma physics processes are reviewed. The two-plasmon-decay instability, stimulated Brillouin scattering (together with cross-beam energy transfer), and (possibly) stimulated Raman scattering are identified as potential concerns, placing constraints on the laser intensities used in target designs, while other processes (self-focusing and filamentation, the parametric decay instability, and magnetic fields), once considered important, are now of lesser concern for mainline direct-drive target concepts. Filamentation is largely suppressed by beam smoothing. Thermal transport modeling, important to the interpretation of experiments and to target design, has been found to be nonlocal in nature. Advances in shock timing and equation-of-state measurements relevant to direct-drive ICF are reported. Room-temperature implosions have provided an increased understanding of the importance of stability and uniformity. The evolution of cryogenic implosion capabilities, leading to an extensive series carried out on the 60-beam OMEGA laser [Boehly et al., Opt. Commun. 133, 495 (1997)], is reviewed together with major advances in cryogenic target formation. A polar-drive concept has been developed that will enable direct-drive-ignition experiments to be performed on the National Ignition Facility [Haynam et al., Appl. Opt. 46(16), 3276 (2007)]. The advantages offered by the alternative approaches of fast ignition and shock ignition and the issues associated with these concepts are described. The lessons learned from target-physics and implosion experiments are taken into account in ignition and high-gain target designs for laser wavelengths of 1/3 μm and 1/4 μm. Substantial advances in direct-drive inertial fusion reactor concepts are reviewed. Overall, the progress in scientific understanding over the past five decades has been enormous, to the point that inertial fusion energy using direct drive shows significant promise as a future environmentally attractive energy source.

Diode-pumped solid-state laser driver experiments for inertial fusion energy applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marshall, C.D.; Payne, S.A.; Emanuel, M.E.

Although solid-state lasers have been the primary means by which the physics of inertial confinement fusion (ICF) have been investigated, it was previously thought that solid-state laser technology could not offer adequate efficiencies for an inertial fusion energy (IFE) power plant. Orth and co-workers have recently designed a conceptual IFE power plant, however, with a high efficiency diode-pumped solid-state laser (DPSSL) driver that utilized several recent innovations in laser technology. It was concluded that DPSSLs could offer adequate performance for IFE with reasonable assumptions. This system was based on a novel diode pumped Yb-doped Sr{sub 5}(PO{sub 4}){sub 3}F (Yb:S-FAP) amplifier.more » Because this is a relatively new gain medium, a project was established to experimentally validate the diode-pumping and extraction dynamics of this system at the smallest reasonable scale. This paper reports on the initial experimental results of this study. We found the pumping dynamics and extraction cross-sections of Yb:S-FAP crystals to be similar to those previously inferred by purely spectroscopic techniques. The saturation fluence for pumping was measured to be 2.2 J/cm{sup 2} using three different methods based on either the spatial, temporal, or energy transmission properties of a Yb:S-FAP rod. The small signal gain implies an emission cross section of 6.0{times}10{sup {minus}20} cm{sup 2}. Up to 1.7 J/cm{sup 3} of stored energy density was achieved in a 6{times}6{times}44 mm{sup 3} Yb:S-FAP amplifier rod. In a free running configuration diode-pumped slope efficiencies up to 43% were observed with output energies up to {approximately}0.5 J per 1 ms pulse from a 3{times}3{times}30 mm{sup 3} rod. When the rod was mounted in a copper block for cooling, 13 W of average power was produced with power supply limited operation at 70 Hz with 500 {mu}s pulses.« less

Qualification of Ti6Al4V ELI Alloy Produced by Laser Powder Bed Fusion for Biomedical Applications

NASA Astrophysics Data System (ADS)

Yadroitsev, I.; Krakhmalev, P.; Yadroitsava, I.; Du Plessis, A.

2018-03-01

Rectangular Ti6Al4V extralow interstitials (ELI) samples were manufactured by laser powder bed fusion (LPBF) in vertical and horizontal orientations relative to the build platform and subjected to various heat treatments. Detailed analyses of porosity, microstructure, residual stress, tensile properties, fatigue, and fracture surfaces were performed based on x-ray micro-computed tomography, scanning electron microscopy, and x-ray diffraction methods. The types of fracture and the tensile fracture mechanisms of the LPBF Ti6Al4V ELI alloy were also studied. Detailed analysis of the microstructure and the corresponding mechanical properties were compared against standard specifications for conventional Ti6Al4V alloy for use in surgical implant applications. Conclusions regarding the mechanical properties and heat treatment of LPBF Ti6Al4V ELI for biomedical applications are made.

Feature-based characterisation of signature topography in laser powder bed fusion of metals

NASA Astrophysics Data System (ADS)

Senin, Nicola; Thompson, Adam; Leach, Richard

2018-04-01

The use of state-of-the-art areal topography measurement instrumentation allows for a high level of detail in the acquisition of topographic information at micrometric scales. The 3D geometric models of surface topography obtained from measured data create new opportunities for the investigation of manufacturing processes through characterisation of the surfaces of manufactured parts. Conventional methods for quantitative assessment of topography usually only involve the computation of texture parameters, summary indicators of topography-related characteristics that are computed over the investigated area. However, further useful information may be obtained through characterisation of signature topographic formations, as more direct indicators of manufacturing process behaviour and performance. In this work, laser powder bed fusion of metals is considered. An original algorithmic method is proposed to isolate relevant topographic formations and to quantify their dimensional and geometric properties, using areal topography data acquired by state-of-the-art areal topography measurement instrumentation.

The use of lasers for achieving extreme conditions of matter, and fusion

NASA Astrophysics Data System (ADS)

Roberts, P. D.

2012-05-01

Since the early'70s AWE has focussed on indirect drive as a means of accessing high energy density regimes. We give a brief historical perspective of this work and the rationale for the construction of the ORION laser. This laser is currently in commissioning and is scheduled to commence experiments in 2012. The ORION laser is configured to provide long pulses (~ 1ns) with a high degree of pulse shape flexibility, together with synchronised short pulse (~1ps) irradiation. The paper describes how this combination should enable pressures in excess of 1 Gb and temperatures of greater than 500 eV to be achieved. The ability to access and diagnose such conditions has applications in many fields; examples are given in planetary science, astrophysics and inertial fusion energy. For these applications we first describe the approach to measuring equation of state and opacity properties in the high energy density regime. Such properties are then incorporated into integrated computer simulation codes and validated against laser experiments, some of which have been conducted recently at the OMEGA laser at the University of Rochester. The paper concludes with a discussion of inertial fusion energy and the new high energy density regimes that this would access, if successful.

Inertial Fusion Target Physics Advantages with the Krypton Fluoride Laser

NASA Astrophysics Data System (ADS)

Obenschain, Stephen

2010-11-01

The krypton fluoride (KrF) laser's short wavelength, broad bandwidth and capability to provide extremely uniform target illumination are advantages towards obtaining high gain direct drive implosions. The short wavelength helps suppress deleterious laser-plasma instabilities, and allows one to employ higher ablation pressures. In addition, the KrF architecture allows one to zoom down the focal diameter to follow the size of the imploding pellet, thereby improving the coupling efficiency. The NRL researchers have been conducting theoretical and experimental studies to quantify the beneficial effects of utilizing KrF light. Experiments using the Nike facility have confirmed that KrF light significantly increases the threshold for laser-plasma instability. This presentation will discuss the observed target physics with KrF light and its effects towards facilitating the high gains needed for power production with inertial fusion. Simulations indicate that shock ignited designs can achieve gains above 200 with KrF energies as low a 1 megajoule. For fusion energy a laser driver must be capable of high repetition rates (5-10 Hz) along with adequate efficiency and durability. The Electra KrF 30-cm aperture electron-beam-pumped amplifier has demonstrated long duration continuous operation at high-repetition rates. This and other advances show that the KrF laser should be able to meet the requirements.

Angular radiation temperature simulation for time-dependent capsule drive prediction in inertial confinement fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jing, Longfei; Yang, Dong; Li, Hang

2015-02-15

The x-ray drive on a capsule in an inertial confinement fusion setup is crucial for ignition. Unfortunately, a direct measurement has not been possible so far. We propose an angular radiation temperature simulation to predict the time-dependent drive on the capsule. A simple model, based on the view-factor method for the simulation of the radiation temperature, is presented and compared with the experimental data obtained using the OMEGA laser facility and the simulation results acquired with VISRAD code. We found a good agreement between the time-dependent measurements and the simulation results obtained using this model. The validated model was thenmore » used to analyze the experimental results from the Shenguang-III prototype laser facility. More specifically, the variations of the peak radiation temperatures at different view angles with the albedo of the hohlraum, the motion of the laser spots, the closure of the laser entrance holes, and the deviation of the laser power were investigated. Furthermore, the time-dependent radiation temperature at different orientations and the drive history on the capsule were calculated. The results indicate that the radiation temperature from “U20W112” (named according to the diagnostic hole ID on the target chamber) can be used to approximately predict the drive temperature on the capsule. In addition, the influence of the capsule on the peak radiation temperature is also presented.« less

A >2-MJ, 1014-W laser system for DT fusion—NIF: a note in celebration of the 75th birthday of Prof. Theodore Haensch

NASA Astrophysics Data System (ADS)

Holzrichter, John F.; Manes, Kenneth R.

2017-01-01

In 1970, Dr. Theodore Haensch joined A.L. Schawlow's group in the physics department at Stanford, as a NATO postdoctoral researcher. Within a short time, he and his colleagues had invented a new, high-resolution, tunable laser system using expanded reflection gratings and an N2 laser for pumping the fluorescing dyes. This work resulted in a high-brightness, high-repetition-rate, narrow-band laser probe for conducting optical spectroscopy at extreme levels of precision. Dr. Haensch, and his many colleagues, particularly Prof. Arthur Schawlow and their students at Stanford, then proceeded to revolutionize optical spectroscopy and to train several generations of exceptional young scientists. At the same time, the Siegman, Harris, and Byer laboratories also at Stanford were making major contributions to the laser and quantum electronics fields. Several students from both groups joined the Livermore Laboratory. That early work, and that of others, encouraged teams at the Lawrence Livermore National Laboratory to design and build a series of increasing complicated, high-power multi-beam laser systems to investigate the potential of laser fusion. The National Ignition Facility, recently completed, is enabling investigations of matter at very high temperatures, T > 1 million K and densities 100-1000× normal. In addition, researchers are creating 1015 DT fusion neutrons per fusion experiment and generating new knowledge about unusual and important conditions of matter.

Method of mounting a fuel pellet in a laser-excited fusion reactor

DOEpatents

Hirsch, Robert L.

1979-01-01

Laser irradiation means for irradiating a target, wherein a single laser light beam from a source and a mirror close to the target are used with aperture means for directing laser light to interact with the target over a broad area of the surface, and for protecting the laser light source.

All-Fiber Laser Curvature Sensor Using an In-Fiber Modal Interferometer Based on a Double Clad Fiber and a Multimode Fiber Structure

PubMed Central

Durán-Sánchez, Manuel; Prieto-Cortés, Patricia; Salceda-Delgado, Guillermo; Castillo-Guzmán, Arturo A.; Selvas-Aguilar, Romeo; Ibarra-Escamilla, Baldemar; Kuzin, Evgeny A.

2017-01-01

An all-fiber curvature laser sensor by using a novel modal interference in-fiber structure is proposed and experimentally demonstrated. The in-fiber device, fabricated by fusion splicing of multimode fiber and double-clad fiber segments, is used as wavelength filter as well as the sensing element. By including a multimode fiber in an ordinary modal interference structure based on a double-clad fiber, the fringe visibility of the filter transmission spectrum is significantly increased. By using the modal interferometer as a curvature sensitive wavelength filter within a ring cavity erbium-doped fiber laser, the spectral quality factor Q is considerably increased. The results demonstrate the reliability of the proposed curvature laser sensor with advantages of robustness, ease of fabrication, low cost, repeatability on the fabrication process and simple operation. PMID:29182527

All-Fiber Laser Curvature Sensor Using an In-Fiber Modal Interferometer Based on a Double Clad Fiber and a Multimode Fiber Structure.

PubMed

Álvarez-Tamayo, Ricardo I; Durán-Sánchez, Manuel; Prieto-Cortés, Patricia; Salceda-Delgado, Guillermo; Castillo-Guzmán, Arturo A; Selvas-Aguilar, Romeo; Ibarra-Escamilla, Baldemar; Kuzin, Evgeny A

2017-11-28

An all-fiber curvature laser sensor by using a novel modal interference in-fiber structure is proposed and experimentally demonstrated. The in-fiber device, fabricated by fusion splicing of multimode fiber and double-clad fiber segments, is used as wavelength filter as well as the sensing element. By including a multimode fiber in an ordinary modal interference structure based on a double-clad fiber, the fringe visibility of the filter transmission spectrum is significantly increased. By using the modal interferometer as a curvature sensitive wavelength filter within a ring cavity erbium-doped fiber laser, the spectral quality factor Q is considerably increased. The results demonstrate the reliability of the proposed curvature laser sensor with advantages of robustness, ease of fabrication, low cost, repeatability on the fabrication process and simple operation.

Low Fuel Convergence Path to Direct-Drive Fusion Ignition

DOE PAGES

Molvig, Kim; Schmitt, Mark J.; Albright, Brian James; ...

2016-06-24

A new class of inertial fusion capsules is presented that combines multishell targets with laser direct drive at low intensity (2.8 × 10 14 W/cm 2) to achieve robust ignition. The targets consist of three concentric, heavy, metal shells, enclosing a volume of tens of μg of liquid deuterium-tritium fuel. Ignition is designed to occur well “upstream” from stagnation, with minimal pusher deceleration to mitigate interface Rayleigh-Taylor growth. As a result, laser intensities below thresholds for laser plasma instability and cross beam energy transfer facilitate high hydrodynamic efficiency (~10%).

Multibeam Stimulated Raman Scattering in Inertial Confinement Fusion Conditions.

PubMed

Michel, P; Divol, L; Dewald, E L; Milovich, J L; Hohenberger, M; Jones, O S; Hopkins, L Berzak; Berger, R L; Kruer, W L; Moody, J D

2015-07-31

Stimulated Raman scattering from multiple laser beams arranged in a cone sharing a common daughter wave is investigated for inertial confinement fusion (ICF) conditions in a inhomogeneous plasma. It is found that the shared electron plasma wave (EPW) process, where the lasers collectively drive the same EPW, can lead to an absolute instability when the electron density reaches a matching condition dependent on the cone angle of the laser beams. This mechanism could explain recent experimental observations of hot electrons at early times in ICF experiments, at densities well below quarter critical when two plasmon decay is not expected to occur.

Prolate-Spheroid (``Rugby-Shaped'') Hohlraum for Inertial Confinement Fusion

NASA Astrophysics Data System (ADS)

Vandenboomgaerde, M.; Bastian, J.; Casner, A.; Galmiche, D.; Jadaud, J.-P.; Laffite, S.; Liberatore, S.; Malinie, G.; Philippe, F.

2007-08-01

A novel rugby-ball shaped hohlraum is designed in the context of the indirect-drive scheme of inertial-confinement fusion (ICF). Experiments were performed on the OMEGA laser and are the first use of rugby hohlraums for ICF studies. Analysis of experimental data shows that the hohlraum energetics is well understood. We show that the rugby-ball shape exhibits advantages over cylinder, in terms of temperature and of symmetry control of the capsule implosion. Simulations indicate that rugby hohlraum driven targets may be candidates for ignition in a context of early Laser MegaJoule experiments with reduced laser energy.

Laser microbeam irradiation and renucleation of mouse eggs. Final progress report, July 1, 1979-December 31, 1983

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, T.P.

1983-01-01

We have combined laser microbeam irradiation of mouse egg nuclei with fusion to donor cell nuclei in order to develop a new procedure for transferring nuclei into mammalian eggs. We have been using virus-treated cells injected into the perivitelline for fusion with egg cells. Binucleate cells inside the zona pellucida were often produced indicating nuclear transfer between cells had occurred. To prevent the formation of such abortive polyploidy, host nuclei were inactivated with a laser microbeam. The subsequent cleavage of the microirradiated eggs has been studied.

The national ignition facility and atomic data

NASA Astrophysics Data System (ADS)

Crandall, David H.

1998-07-01

The National Ignition Facility (NIF) is under construction, capping over 25 years of development of the inertial confinement fusion concept by providing the facility to obtain fusion ignition in the laboratory for the first time. The NIF is a 192 beam glass laser to provide energy controlled in space and time so that a millimeter-scale capsule containing deuterium and tritium can be compressed to fusion conditions. Light transport, conversion of light in frequency, interaction of light with matter in solid and plasma forms, and diagnostics of extreme material conditions on small scale all use atomic data in preparing for use of the NIF. The NIF will provide opportunity to make measurements of atomic data in extreme physical environments related to fusion energy, nuclear weapon detonation, and astrophysics. The first laser beams of NIF should be operational in 2001 and the full facility completed at the end of 2003. NIF is to provide 1.8 megajoule of blue light on fusion targets and is intended to achieve fusion ignition by about the end of 2007. Today's inertial fusion development activities use atomic data to design and predict fusion capsule performance and in non-fusion applications to analyze radiation transport and radiation effects on matter. Conditions investigated involve radiation temperature of hundreds of eV, pressures up to gigabars and time scales of femptoseconds.

A review of laser-plasma interaction physics of indirect-drive fusion

NASA Astrophysics Data System (ADS)

Kirkwood, R. K.; Moody, J. D.; Kline, J.; Dewald, E.; Glenzer, S.; Divol, L.; Michel, P.; Hinkel, D.; Berger, R.; Williams, E.; Milovich, J.; Yin, L.; Rose, H.; MacGowan, B.; Landen, O.; Rosen, M.; Lindl, J.

2013-10-01

The National Ignition Facility (NIF) has been designed, constructed and has recently begun operation to investigate the ignition of nuclear fusion with a laser with up to 1.8 MJ of energy per pulse. The concept for fusion ignition on the NIF, as first proposed in 1990, was based on an indirectly driven spherical capsule of fuel in a high-Z hohlraum cavity filled with low-Z gas (Lindl et al 2004 Phys. Plasmas 11 339). The incident laser energy is converted to x-rays with keV energy on the hohlraums interior wall. The x-rays then impinge on the surface of the capsule, imploding it and producing the fuel conditions needed for ignition. It was recognized at the inception that this approach would potentially be susceptible to scattering of the incident light by the plasma created in the gas and the ablated material in the hohlraum interior. Prior to initial NIF operations, expectations for laser-plasma interaction (LPI) in ignition-scale experiments were based on experimentally benchmarked simulations and models of the plasma effects that had been carried out as part of the original proposal for NIF and expanded during the 13-year design and construction period. The studies developed the understanding of the stimulated Brillouin scatter, stimulated Raman scatter and filamentation that can be driven by the intense beams. These processes produce scatter primarily in both the forward and backward direction, and by both individual beams and collective interaction of multiple beams. Processes such as hot electron production and plasma formation and transport were also studied. The understanding of the processes so developed was the basis for the design and planning of the recent experiments in the ignition campaign at NIF, and not only indicated that the plasma instabilities could be controlled to maximize coupling, but predicted that, for the first time, they would be beneficial in controlling drive symmetry. The understanding is also now a critical component in the worldwide effort to produce a fusion energy source with a laser (Lindl et al 2011 Nucl. Fusion 51 094024, Collins et al 2012 Phys. Plasmas 19 056308) and has recently received its most critical test yet with the inception of the NIF experiments with ignition-scale indirect-drive targets (Landen et al 2010 Phys. Plasmas 17 056301, Edwards et al 2011 Phys. Plasmas 18 051003, Glenzer et al 2011 Phys. Rev. Lett. 106 085004, Haan et al 2011 Phys. Plasmas 18 051001, Landen et al 2011 Phys. Plasmas 18 051001, Lindl et al 2011 Nucl. Fusion 51 094024). In this paper, the data obtained in the first complete series of coupling experiments in ignition-scale hohlraums is reviewed and compared with the preceding work on the physics of LPIs with the goal of recognizing aspects of our understanding that are confirmed by these experiments and recognizing and motivating areas that need further modeling. Understanding these hohlraum coupling experiments is critical as they are only the first step in a campaign to study indirectly driven implosions under the conditions of ignition by inertial confinement at NIF, and in the near future they are likely to further influence ignition plans and experimental designs.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Structure and properties of aluminum-silicon alloys hardened locally by concentrated energy sources

NASA Astrophysics Data System (ADS)

Voronin, S. V.; Gureev, D. M.; Zolotarevskiĭ, A. V.

1990-06-01

An investigation was made of some characteristics of the formation of the structure of Al-Si alloys containing 10%, 12% and 20 % Si, and also of the commercial alloy V124 under conditions of surface fusion by laser-arc and laser sources. It was established that as a result of local fusion there was a change in the silicon deposition morphology, the α solid solution became oversaturated, and the eutectic point was shifted toward high silicon concentrations. It was found that the hardened layer retained its high hardness when treated at temperatures up to 250 °C. The commercial alloy V124 was used as an example to show that an alloyed layer with a controlled silicon concentration can be obtained on the surface by using a laser-arc or laser source.

Efficient source for the production of ultradense deuterium D(-1) for laser-induced fusion (ICF).

PubMed

Andersson, Patrik U; Lönn, Benny; Holmlid, Leif

2011-01-01

A novel source which simplifies the study of ultradense deuterium D(-1) is now described. This means one step further toward deuterium fusion energy production. The source uses internal gas feed and D(-1) can now be studied without time-of-flight spectral overlap from the related dense phase D(1). The main aim here is to understand the material production parameters, and thus a relatively weak laser with focused intensity ≤10(12) W cm(-2) is employed for analyzing the D(-1) material. The properties of the D(-1) material at the source are studied as a function of laser focus position outside the emitter, deuterium gas feed, laser pulse repetition frequency and laser power, and temperature of the source. These parameters influence the D(-1) cluster size, the ionization mode, and the laser fragmentation patterns.

Imposed magnetic field and hot electron propagation in inertial fusion hohlraums

DOE PAGES

Strozzi, David J.; Perkins, L. J.; Marinak, M. M.; ...

2015-12-02

The effects of an imposed, axial magnetic fieldmore » $$B_{z0}$$ on hydrodynamics and energetic electrons in inertial confinement fusion indirect-drive hohlraums are studied. We present simulations from the radiation-hydrodynamics code HYDRA of a low-adiabat ignition design for the National Ignition Facility, with and without $$B_{z0}=70~\\text{T}$$. The field’s main hydrodynamic effect is to significantly reduce electron thermal conduction perpendicular to the field. This results in hotter and less dense plasma on the equator between the capsule and hohlraum wall. The inner laser beams experience less inverse bremsstrahlung absorption before reaching the wall. The X-ray drive is thus stronger from the equator with the imposed field. We study superthermal, or ‘hot’, electron dynamics with the particle-in-cell code ZUMA, using plasma conditions from HYDRA. During the early-time laser picket, hot electrons based on two-plasmon decay in the laser entrance hole (Regan et al., Phys. Plasmas, vol. 17(2), 2010, 020703) are guided to the capsule by a 70 T field. Twelve times more energy deposits in the deuterium–tritium fuel. For plasma conditions early in peak laser power, we present mono-energetic test-case studies with ZUMA as well as sources based on inner-beam stimulated Raman scattering. Furthermore, the effect of the field on deuterium–tritium deposition depends strongly on the source location, namely whether hot electrons are generated on field lines that connect to the capsule.« less

Microstructure and Solidification Crack Susceptibility of Al 6014 Molten Alloy Subjected to a Spatially Oscillated Laser Beam.

PubMed

Kang, Minjung; Han, Heung Nam; Kim, Cheolhee

2018-04-23

Oscillating laser beam welding for Al 6014 alloy was performed using a single mode fiber laser and two-axis scanner system. Its effect on the microstructural evolution of the fusion zone was investigated. To evaluate the influence of oscillation parameters, self-restraint test specimens were fabricated with different beam patterns, widths, and frequencies. The behavior of hot cracking propagation was analyzed by high-speed camera and electron backscatter diffraction. The behavior of crack propagation was observed to be highly correlated with the microstructural evolution of the fusion zone. For most oscillation conditions, the microstructure resembled that of linear welds. A columnar structure was formed near the fusion line and an equiaxed structure was generated at its center. The wide equiaxed zone of oscillation welding increased solidification crack susceptibility. For an oscillation with an infinite-shaped scanning pattern at 100 Hz and 3.5 m/min welding speed, the bead width, solidification microstructure, and the width of the equiaxed zone at the center of fusion fluctuated. Furthermore, the equiaxed and columnar regions alternated periodically, which could reduce solidification cracking susceptibility.

Microstructure and Solidification Crack Susceptibility of Al 6014 Molten Alloy Subjected to a Spatially Oscillated Laser Beam

PubMed Central

Kang, Minjung; Han, Heung Nam

2018-01-01

Oscillating laser beam welding for Al 6014 alloy was performed using a single mode fiber laser and two-axis scanner system. Its effect on the microstructural evolution of the fusion zone was investigated. To evaluate the influence of oscillation parameters, self-restraint test specimens were fabricated with different beam patterns, widths, and frequencies. The behavior of hot cracking propagation was analyzed by high-speed camera and electron backscatter diffraction. The behavior of crack propagation was observed to be highly correlated with the microstructural evolution of the fusion zone. For most oscillation conditions, the microstructure resembled that of linear welds. A columnar structure was formed near the fusion line and an equiaxed structure was generated at its center. The wide equiaxed zone of oscillation welding increased solidification crack susceptibility. For an oscillation with an infinite-shaped scanning pattern at 100 Hz and 3.5 m/min welding speed, the bead width, solidification microstructure, and the width of the equiaxed zone at the center of fusion fluctuated. Furthermore, the equiaxed and columnar regions alternated periodically, which could reduce solidification cracking susceptibility. PMID:29690630

DOE Office of Scientific and Technical Information (OSTI.GOV)

Spaeth, M. L.; Manes, K. R.; Kalantar, D. H.

The possibility of imploding small capsules to produce mini-fusion explosions was explored soon after the first thermonuclear explosions in the early 1950s. Various technologies have been pursued to achieve the focused power and energy required for laboratory-scale fusion. Each technology has its own challenges. For example, electron and ion beams can deliver the large amounts of energy but must contend with Coulomb repulsion forces that make focusing these beams a daunting challenge. The demonstration of the first laser in 1960 provided a new option. Energy from laser beams can be focused and deposited within a small volume; the challenge becamemore » whether a practical laser system can be constructed that delivers the power and energy required while meeting all other demands for achieving a high-density, symmetric implosion. The National Ignition Facility (NIF) is the laser designed and built to meet the challenges for study of high-energy-density physics and inertial confinement fusion (ICF) implosions. This study describes the architecture, systems, and subsystems of NIF. Finally, it describes how they partner with each other to meet these new, complex demands and describes how laser science and technology were woven together to bring NIF into reality.« less

Characterization of inertial confinement fusion (ICF) targets using PIXE, RBS, and STIM analysis.

PubMed

Li, Yongqiang; Liu, Xue; Li, Xinyi; Liu, Yiyang; Zheng, Yi; Wang, Min; Shen, Hao

2013-08-01

Quality control of the inertial confinement fusion (ICF) target in the laser fusion program is vital to ensure that energy deposition from the lasers results in uniform compression and minimization of Rayleigh-Taylor instabilities. The technique of nuclear microscopy with ion beam analysis is a powerful method to provide characterization of ICF targets. Distribution of elements, depth profile, and density image of ICF targets can be identified by particle-induced X-ray emission, Rutherford backscattering spectrometry, and scanning transmission ion microscopy. We present examples of ICF target characterization by nuclear microscopy at Fudan University in order to demonstrate their potential impact in assessing target fabrication processes.

NRL Review 2005. Pioneering the Future

DTIC Science & Technology

2005-01-01

pulse high- intensity lasers —the Table-Top Terawatt (T3) laser and the new Ti:Sapphire Femtosecond Laser (TFL)—to study intense laser -plasma...56 laser beams and is single- pulsed (4-ns pulse ). This facility provides intense radiation for studying inertial confinement fusion (ICF) target... ultrashort - pulse (40 fs), Ti:Sapphire Fem- tosecond Laser (TFL) system is now operational at 1 TW. These lasers comprise a

A feasibility study of a NBI photoneutralizer based on nonlinear gating laser recirculation

NASA Astrophysics Data System (ADS)

Fassina, A.; Pretato, F.; Barbisan, M.; Giudicotti, L.; Pasqualotto, R.

2016-02-01

The neutralization efficiency of negative ion neutral beam injectors is a major issue for future fusion reactors. Photon neutralization might be a valid alternative to present gas neutralizers, but still with several challenges for a valid implementation. Some concepts have been presented so far but none has been validated yet. A novel photoneutralization concept is discussed here, based on an annular cavity and a duplicated frequency laser beam (recirculation injection by nonlinear gating). The choice of lithium triborate as the material for the second harmonic extractor is discussed and a possible cooling method via crystal slicing is presented; laser intensity enhancement within the cavity is evaluated in order to quantify the achievable neutralization rate. Mockups of the critical components are proposed as intermediate steps toward system realization.

Deuteron Beam Driven Fast Ignition of a Pre-Compressed Inertial Confinement Fusion (ICF) Fuel Capsule

NASA Astrophysics Data System (ADS)

Yang, Xiaoling; Miley, George; Flippo, Kirk; Hora, Heinrich; Gaillard, Sandrine; Offermann, Dustin

2012-10-01

We proposed to utilize a new ``Deuterium Cluster'' type structure for the laser interaction foil to generate an energetic deuteron beam as the fast igniter to ignite inertial confinement fusion fuel capsule. The benefit of deuteron beam driven fast ignition is that its deposition in the target fuel will not only provide heating but also fuse with fuel as they slow down in the target. The preliminary results from recent laser-deuteron acceleration experiment at LANL were encouraging. Also, in most recent calculations, we found that a 12.73% extra energy gain from deuteron beam-target fusion could be achieved when quasi-Maxwellian deuteron beam was assumed, and when a ρrb = 4.5 g/cm2 was considered, where ρ is the fuel density, and rb is the ion beam focusing radius on the target. These results provide some insight into the contribution of the extra heat produced by deuteron beam-target fusion to the hot spot ignition process. If the physics works as anticipated, this novel type of interaction foil can efficiently generate energetic deuterons during intense laser pulses. The massive yield of deuterons should turn out to be the most efficient way of igniting the DT fuel, making the dream of near-term commercialization of FI fusion more achievable.

Microstructure and Mechanical Properties of Fiber-Laser-Welded and Diode-Laser-Welded AZ31 Magnesium Alloy

NASA Astrophysics Data System (ADS)

Chowdhury, S. M.; Chen, D. L.; Bhole, S. D.; Powidajko, E.; Weckman, D. C.; Zhou, Y.

2011-07-01

The microstructures, tensile properties, strain hardening, and fatigue strength of fiber-laser-welded (FLW) and diode-laser-welded (DLW) AZ31B-H24 magnesium alloys were studied. Columnar dendrites near the fusion zone (FZ) boundary and equiaxed dendrites at the center of FZ, with divorced eutectic β-Mg17Al12 particles, were observed. The FLW joints had smaller dendrite cell sizes with a narrower FZ than the DLW joints. The heat-affected zone consisted of recrystallized grains. Although the DLW joints fractured at the center of FZ and exhibited lower yield strength (YS), ultimate tensile strength (UTS), and fatigue strength, the FLW joints failed at the fusion boundary and displayed only moderate reduction in the YS, UTS, and fatigue strength with a joint efficiency of ~91 pct. After welding, the strain rate sensitivity basically vanished, and the DLW joints exhibited higher strain-hardening capacity. Stage III hardening occurred after yielding in both base metal (BM) and welded samples. Dimple-like ductile fracture characteristics appeared in the BM, whereas some cleavage-like flat facets together with dimples and river marking were observed in the welded samples. Fatigue crack initiated from the specimen surface or near-surface defects, and crack propagation was characterized by the formation of fatigue striations along with secondary cracks.

Laser targets compensate for limitations in inertial confinement fusion drivers

NASA Astrophysics Data System (ADS)

Kilkenny, J. D.; Alexander, N. B.; Nikroo, A.; Steinman, D. A.; Nobile, A.; Bernat, T.; Cook, R.; Letts, S.; Takagi, M.; Harding, D.

2005-10-01

Success in inertial confinement fusion (ICF) requires sophisticated, characterized targets. The increasing fidelity of three-dimensional (3D), radiation hydrodynamic computer codes has made it possible to design targets for ICF which can compensate for limitations in the existing single shot laser and Z pinch ICF drivers. Developments in ICF target fabrication technology allow more esoteric target designs to be fabricated. At present, requirements require new deterministic nano-material fabrication on micro scale.

Conceptual design considerations and neutronics of lithium fall laser fusion target chambers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meier, W.R.; Thomson, W.B.

1978-05-31

Atomics International and Lawrence Livermore Laboratory are involved in the conceptual design of a laser fusion power plant incorporating the lithium fall target chamber. In this paper we discuss some of the more important design considerations for the target chamber and evaluate its nuclear performance. Sizing and configuration of the fall, hydraulic effects, and mechanical design considerations are addressed. The nuclear aspects examined include tritium breeding, energy deposition, and radiation damage.

Post-modelling of images from a laser-induced wavy boiling front

NASA Astrophysics Data System (ADS)

Matti, R. S.; Kaplan, A. F. H.

2015-12-01

Processes like laser keyhole welding, remote fusion laser cutting or laser drilling are governed by a highly dynamic wavy boiling front that was recently recorded by ultra-high speed imaging. A new approach has now been established by post-modelling of the high speed images. Based on the image greyscale and on a cavity model the three-dimensional front topology is reconstructed. As a second step the Fresnel absorptivity modulation across the wavy front is calculated, combined with the local projection of the laser beam. Frequency polygons enable additional analysis of the statistical variations of the properties across the front. Trends like shadow formation and time dependency can be studied, locally and for the whole front. Despite strong topology modulation in space and time, for lasers with 1 μm wavelength and steel the absorptivity is bounded to a narrow range of 35-43%, owing to its Fresnel characteristics.

Refractive Index Seen by a Probe Beam Interacting with a Laser-Plasma System

DOE PAGES

Turnbull, D.; Goyon, C.; Kemp, G. E.; ...

2017-01-05

Here, we report the first complete set of measurements of a laser-plasma optical system’s refractive index, as seen by a second probe laser beam, as a function of the relative wavelength shift between the two laser beams. Both the imaginary and real refractive index components are found to be in good agreement with linear theory using plasma parameters measured by optical Thomson scattering and interferometry; the former is in contrast to previous work and has implications for crossed-beam energy transfer in indirect-drive inertial confinement fusion, and the latter is measured for the first time. The data include the first demonstrationmore » of a laser-plasma polarizer with 85$-$87% extinction for the particular laser and plasma parameters used in this experiment, complementing the existing suite of high-power, tunable, and ultrafast plasma-based photonic devices.« less

Fusion of 3D laser scanner and depth images for obstacle recognition in mobile applications

NASA Astrophysics Data System (ADS)

Budzan, Sebastian; Kasprzyk, Jerzy

2016-02-01

The problem of obstacle detection and recognition or, generally, scene mapping is one of the most investigated problems in computer vision, especially in mobile applications. In this paper a fused optical system using depth information with color images gathered from the Microsoft Kinect sensor and 3D laser range scanner data is proposed for obstacle detection and ground estimation in real-time mobile systems. The algorithm consists of feature extraction in the laser range images, processing of the depth information from the Kinect sensor, fusion of the sensor information, and classification of the data into two separate categories: road and obstacle. Exemplary results are presented and it is shown that fusion of information gathered from different sources increases the effectiveness of the obstacle detection in different scenarios, and it can be used successfully for road surface mapping.

Dependence of the critical temperature of laser-ablated YBa2Cu3O(7-delta) thin films on LaAlO3 substrate growth technique

NASA Technical Reports Server (NTRS)

Warner, Joseph D.; Bhasin, Kul B.; Miranda, Felix A.

1991-01-01

Samples of LaAlO3 made by flame fusion and Czochralski method were subjected to the same temperature conditions that they have to undergo during the laser ablation deposition of YBa2Cu3O(7 - delta) thin films. After oxygen annealing at 750 C, the LaAlO3 substrate made by two methods experienced surface roughening. The degree of roughening on the substrate made by Czochralski method was three times greater than that on the substrate made by flame fusion. This excessive surface roughening may be the origin of the experimentally observed lowering of the critical temperature of a film deposited by laser ablation on a LaAlO3 substrate made by Czochralski method with respect to its counterpart deposited on LaAlO3 substrates made by flame fusion.

Method of making foam-encapsulated laser targets

DOEpatents

Rinde, James A.; Fulton, Fred J.

1977-01-01

Foam-encapsulated laser fusion targets are fabricated by suspending fusion fuel filled shells in a solution of cellulose acetate, extruding the suspension through a small orifice into a bath of ice water, soaking the thus formed shell containing cellulose acetate gel in the water to extract impurities, freezing the gel, and thereafter freeze-drying wherein water and solvents sublime and the gel structure solidifies into a low-density microcellular foam containing one or more encapsulated fuel-filled shells. The thus formed material is thereafter cut and mounted on a support to provide laser fusion targets containing a fuel-filled shell surrounded by foam having a thickness of 10 to 60 .mu.m, a cell size of less than 2 .mu.m, and density of 0.08 to 0.6.times.10.sup.3 kg/m.sup.3. Various configured foam-encapsulated targets capable of being made by the encapsulation method are illustrated.

Laser Fusion - A New Thermonuclear Concept

ERIC Educational Resources Information Center

Cooper, Ralph S.

1975-01-01

Describes thermonuclear processes induced by interaction of a laser beam with the surface of a fuel pellet. An expanding plasma is formed which results in compression of the element. Laser and reactor technology are discussed. Pictures and diagrams are included. (GH)

Study on polarization image methods in turbid medium

NASA Astrophysics Data System (ADS)

Fu, Qiang; Mo, Chunhe; Liu, Boyu; Duan, Jin; Zhang, Su; Zhu, Yong

2014-11-01

Polarization imaging detection technology in addition to the traditional imaging information, also can get polarization multi-dimensional information, thus improve the probability of target detection and recognition.Image fusion in turbid medium target polarization image research, is helpful to obtain high quality images. Based on visible light wavelength of light wavelength of laser polarization imaging, through the rotation Angle of polaroid get corresponding linear polarized light intensity, respectively to obtain the concentration range from 5% to 10% of turbid medium target stocks of polarization parameters, introduces the processing of image fusion technology, main research on access to the polarization of the image by using different polarization image fusion methods for image processing, discusses several kinds of turbid medium has superior performance of polarization image fusion method, and gives the treatment effect and analysis of data tables. Then use pixel level, feature level and decision level fusion algorithm on three levels of information fusion, DOLP polarization image fusion, the results show that: with the increase of the polarization Angle, polarization image will be more and more fuzzy, quality worse and worse. Than a single fused image contrast of the image be improved obviously, the finally analysis on reasons of the increase the image contrast and polarized light.

Interplay of Laser-Plasma Interactions and Inertial Fusion Hydrodynamics

DOE PAGES

Strozzi, D. J.; Bailey, D. S.; Michel, P.; ...

2017-01-12

The effects of laser-plasma interactions (LPI) on the dynamics of inertial confinement fusion hohlraums are investigated in this work via a new approach that self-consistently couples reduced LPI models into radiation-hydrodynamics numerical codes. The interplay between hydrodynamics and LPI—specifically stimulated Raman scatter and crossed-beam energy transfer (CBET)—mostly occurs via momentum and energy deposition into Langmuir and ion acoustic waves. This spatially redistributes energy coupling to the target, which affects the background plasma conditions and thus, modifies laser propagation. In conclusion, this model shows reduced CBET and significant laser energy depletion by Langmuir waves, which reduce the discrepancy between modeling andmore » data from hohlraum experiments on wall x-ray emission and capsule implosion shape.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chicklis, E.P.; Folweiler, R.C.; Pollak, T.M.

This is a combined study of resonant pumped solid state lasers as fusion drivers, and the development of crystalline optical materials suitable for propagation of the high peak powers associated with laser fusion research. During this period of study the concept of rare gas halide lasers was first demonstrated by the lasing of Tm:YLF at 453 nm pumped by the 353 nm energy of XeF. Excited stata densities of 5 x 10/sup 18/ cm/sup -3/ have been attained and spectroscopic measurements show that up to 60% of the pump energy can be converted into useful stored energy. Alternative lasers andmore » pumping schemes are also discussed. In all cases the potential RGH/SS systems are evaluated in respect to internal efficiency and heat loading.« less

Modelling the thermomechanical behaviour of the tungsten first wall in HiPER laser fusion scenarios

NASA Astrophysics Data System (ADS)

Garoz, D.; Páramo, A. R.; Rivera, A.; Perlado, J. M.; González-Arrabal, R.

2016-12-01

The behaviour of a tungsten first wall is studied under the irradiation conditions predicted for the different operational scenarios of the European laser fusion project HiPER, which is based on direct drive targets and an evacuated dry wall chamber. The scenarios correspond to different stages in the development of a nuclear fusion reactor, from proof of principle (bunch mode facility) to economic feasibility (pre-commercial power plant). This work constitutes a quantitative study to evaluate first wall performance under realistic irradiation conditions in the different scenarios. We calculated the radiation fluxes assuming the geometrical configurations reported so far for HiPER. Then, we calculated the irradiation-induced evolution of first wall temperature and the thermomechanical response of the material. The results indicate that the first wall will plastically deform up to a few microns underneath the surface. Continuous operation in a power plant leads to fatigue failure with crack generation and growth. Finally, crack propagation and the minimum tungsten thickness required to fulfil the first wall protection role is studied. The response of tungsten as a first wall material as well as its main limitations will be discussed for the HiPER scenarios.

Investigation on microstructure and properties of narrow-gap laser welding on reduced activation ferritic/martensitic steel CLF-1 with a thickness of 35 mm

NASA Astrophysics Data System (ADS)

Wu, Shikai; Zhang, Jianchao; Yang, Jiaoxi; Lu, Junxia; Liao, Hongbin; Wang, Xiaoyu

2018-05-01

Reduced activation ferritic martensitic (RAFM) steel is chosen as a structural material for test blanket modules (TBMs) to be constructed in International Thermonuclear Experimental Reactor (ITER) and China Fusion Engineering Test Reactor (CFETR). Chinese specific RAFM steel named with CLF-1 has been developed for CFETR. In this paper, a narrow-gap groove laser multi-pass welding of CLF-1 steel with thickness of 35 mm is conduced by YLS-15000 fiber laser. Further, the microstructures of different regions in the weld joint were characterized, and tensile impact and micro-hardness tests were carried out for evaluating the mecharical properties. The results show that the butt weld joint of CLF-1 steel with a thickness of 35 mm was well-formed using the optimal narrow-gap laser filler wire welding and no obvious defects was found such as incomplete fusion cracks and pores. The microstructures of backing layer is dominated by lath martensites and the Heat-Affected Zone (HAZ) was mainly filled with two-phase hybrid structures of secondary-tempering sorbites and martensites. The filler layer is similar to the backing layer in microstructures. In tensile tests, the tensile samples from different parts of the joint all fractured at base metal (BM). The micro-hardness of weld metal (WM) was found to be higher than that of BM and the Heat-Affected Zone (HAZ) exhibited no obvious softening. After post weld heat treatment (PWHT), it can be observed that the fusion zone of the autogenous welding bead and the upper filling beads mainly consist of lath martensites which caused the lower impact absorbing energy. The HAZ mainly included two-phase hybrid structures of secondary-tempering sorbites and martensites and exhibited favorable impact toughness.

Influence of laser induced hot electrons on the threshold for shock ignition of fusion reactions

NASA Astrophysics Data System (ADS)

Colaïtis, A.; Ribeyre, X.; Le Bel, E.; Duchateau, G.; Nicolaï, Ph.; Tikhonchuk, V.

2016-07-01

The effects of Hot Electrons (HEs) generated by the nonlinear Laser-Plasma Interaction (LPI) on the dynamics of Shock Ignition Inertial Confinement Fusion targets are investigated. The coupling between the laser beam, plasma dynamics and hot electron generation and propagation is described with a radiative hydrodynamics code using an inline model based on Paraxial Complex Geometrical Optics [Colaïtis et al., Phys. Rev. E 92, 041101 (2015)]. Two targets are considered: the pure-DT HiPER target and a CH-DT design with baseline spike powers of the order of 200-300 TW. In both cases, accounting for the LPI-generated HEs leads to non-igniting targets when using the baseline spike powers. While HEs are found to increase the ignitor shock pressure, they also preheat the bulk of the imploding shell, notably causing its expansion and contamination of the hotspot with the dense shell material before the time of shock convergence. The associated increase in hotspot mass (i) increases the ignitor shock pressure required to ignite the fusion reactions and (ii) significantly increases the power losses through Bremsstrahlung X-ray radiation, thus rapidly cooling the hotspot. These effects are less prominent for the CH-DT target where the plastic ablator shields the lower energy LPI-HE spectrum. Simulations using higher laser spike powers of 500 TW suggest that the CH-DT capsule marginally ignites, with an ignition window width significantly smaller than without LPI-HEs, and with three quarters of the baseline target yield. The latter effect arises from the relation between the shock launching time and the shell areal density, which becomes relevant in presence of a LPI-HE preheating.

Development of high-average-power DPSSL with high beam quality

NASA Astrophysics Data System (ADS)

Nakai, Sadao; Kanabe, Tadashi; Kawashima, Toshiyuki; Yamanaka, Masanobu; Izawa, Yasukazu; Nakatuka, Masahiro; Kandasamy, Ranganathan; Kan, Hirofumi; Hiruma, Teruo; Niino, Masayuki

2000-08-01

The recent progress of high power diode laser is opening new fields of laser and its application. We are developing high average power diode pumped solid state laser DPSSL for laser fusion power plant, for space propulsion and for various applications in industry. The common features or requirements of our High Average-power Laser for Nuclear-fusion Application (HALNA) are large pulse energy with relatively low repetition of few tens Hz, good beam quality of order of diffraction limit and high efficiency more than 10%. We constructed HALNA 10 (10J X 10 Hz) and tested the performance to clarify the scalability to higher power system. We have obtained in a preliminary experiment a 8.5 J output energy at 0.5 Hz with beam quality of 2 times diffraction limited far-field pattern.

Nuclear Fusion induced by Coulomb Explosion of Heteronuclear Clusters

NASA Astrophysics Data System (ADS)

Last, Isidore; Jortner, Joshua

2001-07-01

We propose a new mechanism for the production of high-energy ( E>3 keV) deuterons, suitable to induce dd nuclear fusion, based on multielectron ionization and Coulomb explosion of heteronuclear deuterium containing molecular clusters, e.g., (D2O)n, in intense ( 1016-2×1018 W/cm2) laser fields. Cluster size equations for E, in conjunction with molecular dynamics simulations, reveal important advantages of Coulomb explosion of (D2O)n heteronuclear clusters, as compared with (D)n clusters. These involve the considerably increased D+ kinetic energy and a narrow, high-energy distribution of deuterons.

Laser erosion diagnostics of plasma facing materials with displacement sensors and their application to safeguard monitors to protect nuclear fusion chambers

NASA Astrophysics Data System (ADS)

Kasuya, Koichi; Motokoshi, Shinji; Taniguchi, Seiji; Nakai, Mitsuo; Tokunaga, Kazutoshi; Mroz, Waldemar; Budner, Boguslaw; Korczyc, Barbara

2015-02-01

Tungsten and SiC are candidates for the structural materials of the nuclear fusion reactor walls, while CVD poly-crystal diamond is candidate for the window material under the hazardous fusion stresses. We measured the surface endurance strength of such materials with commercial displacement sensors and our recent evaluation method. The pulsed high thermal input was put into the material surfaces by UV lasers, and the surface erosions were diagnosed. With the increase of the total number of the laser shots per position, the crater depth increased gradually. The 3D and 2D pictures of the craters were gathered and compared under various experimental conditions. For example, the maximum crater depths were plotted as a function of shot accumulated numbers, from which we evaluated the threshold thermal input for the surface erosions to be induced. The simple comparison-result showed that tungsten was stronger roughly two times than SiC. Then we proposed how to monitor the surface conditions of combined samples with such diamonds coated with thin tungsten layers, when we use such samples as parts of divertor inner walls, fusion chamber first walls, and various diagnostic windows. We investigated how we might be able to measure the inner surface erosions with the same kinds of displacement sensors. We found out the measurable maximum thickness of such diamond which is useful to monitor the erosion. Additionally we showed a new scheme of fusion reactor systems with injectors for anisotropic pellets and heating lasers under the probable use of W and/or SiC.

Stabilization effect of Weibel modes in relativistic laser fusion plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belghit, Slimen, E-mail: Belghit.slimen@gmail.com; Sid, Abdelaziz, E-mail: Sid-abdelaziz@hotmail.com

In this work, the Weibel instability (WI) due to inverse bremsstrahlung (IB) absorption in a laser fusion plasma has been investigated. The stabilization effect due to the coupling of the self-generated magnetic field by WI with the laser wave field is explicitly shown. In this study, the relativistic effects are taken into account. Here, the basic equation is the relativistic Fokker-Planck (F-P) equation. The main obtained result is that the coupling of self-generated magnetic field with the laser wave causes a stabilizing effect of excited Weibel modes. We found a decrease in the spectral range of Weibel unstable modes. Thismore » decreasing is accompanied by a reduction of two orders in the growth rate of instable Weibel modes or even stabilization of these modes. It has been shown that the previous analysis of the Weibel instability due to IB has overestimated the values of the generated magnetic fields. Therefore, the generation of magnetic fields by the WI due to IB should not affect the experiences of an inertial confinement fusion.« less

Identifying and Tracking Pedestrians Based on Sensor Fusion and Motion Stability Predictions

PubMed Central

Musleh, Basam; García, Fernando; Otamendi, Javier; Armingol, José Mª; de la Escalera, Arturo

2010-01-01

The lack of trustworthy sensors makes development of Advanced Driver Assistance System (ADAS) applications a tough task. It is necessary to develop intelligent systems by combining reliable sensors and real-time algorithms to send the proper, accurate messages to the drivers. In this article, an application to detect and predict the movement of pedestrians in order to prevent an imminent collision has been developed and tested under real conditions. The proposed application, first, accurately measures the position of obstacles using a two-sensor hybrid fusion approach: a stereo camera vision system and a laser scanner. Second, it correctly identifies pedestrians using intelligent algorithms based on polylines and pattern recognition related to leg positions (laser subsystem) and dense disparity maps and u-v disparity (vision subsystem). Third, it uses statistical validation gates and confidence regions to track the pedestrian within the detection zones of the sensors and predict their position in the upcoming frames. The intelligent sensor application has been experimentally tested with success while tracking pedestrians that cross and move in zigzag fashion in front of a vehicle. PMID:22163639

Identifying and tracking pedestrians based on sensor fusion and motion stability predictions.

PubMed

Musleh, Basam; García, Fernando; Otamendi, Javier; Armingol, José Maria; de la Escalera, Arturo

2010-01-01

The lack of trustworthy sensors makes development of Advanced Driver Assistance System (ADAS) applications a tough task. It is necessary to develop intelligent systems by combining reliable sensors and real-time algorithms to send the proper, accurate messages to the drivers. In this article, an application to detect and predict the movement of pedestrians in order to prevent an imminent collision has been developed and tested under real conditions. The proposed application, first, accurately measures the position of obstacles using a two-sensor hybrid fusion approach: a stereo camera vision system and a laser scanner. Second, it correctly identifies pedestrians using intelligent algorithms based on polylines and pattern recognition related to leg positions (laser subsystem) and dense disparity maps and u-v disparity (vision subsystem). Third, it uses statistical validation gates and confidence regions to track the pedestrian within the detection zones of the sensors and predict their position in the upcoming frames. The intelligent sensor application has been experimentally tested with success while tracking pedestrians that cross and move in zigzag fashion in front of a vehicle.

Local zone-wise elastic-plastic constitutive parameters of Laser-welded aluminium alloy 6061 using digital image correlation

NASA Astrophysics Data System (ADS)

Bai, Ruixiang; Wei, Yuepeng; Lei, Zhenkun; Jiang, Hao; Tao, Wang; Yan, Cheng; Li, Xiaolei

2018-02-01

The mechanical properties of aluminium alloys can be affected by the local high temperature in laser welding. In this paper, an inversion identification method of local zone-wise elastic-plastic constitutive parameters for laser welding of aluminium alloy 6061 was proposed based on full-field optical measurement data using digital image correlation (DIC). Three regions, i.e., the fusion zone, heat-affected zone, and base zone, of the laser-welded joint were distinguished by means of microstructure optical observation and micrometer hardness measurement. The stress data were obtained using a laser-welded specimen via a uniaxial tensile test. Meanwhile, the local strain data of the laser-welded specimen were obtained by the DIC technique. Thus, the stress-strain relationship for different local regions was established. Finally, the constitutive parameters of the Ramberg-Osgood model were identified by least-square fitting to the experimental stress-strain data. Experimental results revealed that the mechanical properties of the local zones of the welded joints clearly weakened, and these results are consistent with the results of the hardness measurement.

Environmental sensing with optical fiber sensors processed with focused ion beam and atomic layer deposition

NASA Astrophysics Data System (ADS)

Flores, Raquel; Janeiro, Ricardo; Dahlem, Marcus; Viegas, Jaime

2015-03-01

We report an optical fiber chemical sensor based on a focused ion beam processed optical fiber. The demonstrated sensor is based on a cavity formed onto a standard 1550 nm single-mode fiber by either chemical etching, focused ion beam milling (FIB) or femtosecond laser ablation, on which side channels are drilled by either ion beam milling or femtosecond laser irradiation. The encapsulation of the cavity is achieved by optimized fusion splicing onto a standard single or multimode fiber. The empty cavity can be used as semi-curved Fabry-Pérot resonator for gas or liquid sensing. Increased reflectivity of the formed cavity mirrors can be achieved with atomic layer deposition (ALD) of alternating metal oxides. For chemical selective optical sensors, we demonstrate the same FIB-formed cavity concept, but filled with different materials, such as polydimethylsiloxane (PDMS), poly(methyl methacrylate) (PMMA) which show selective swelling when immersed in different solvents. Finally, a reducing agent sensor based on a FIB formed cavity partially sealed by fusion splicing and coated with a thin ZnO layer by ALD is presented and the results discussed. Sensor interrogation is achieved with spectral or multi-channel intensity measurements.

System study of a diode-pumped solid-state-laser driver for inertial fusion energy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orth, C.D.; Payne, S.A.

The present a conceptual design of a diode-pumped solid-state-laser (DPSSL) driver for an inertial fusion energy (IFE) power plant based on the maximized cost of electricity (COE) as determined in a comprehensive systems study. This study contained extensive detail for all significant DPSSL physics and costs, plus published scaling relationships for the costs of the target chamber and the balance of plant (BOP). Our DPSSL design offers low development cost because it is modular, can be fully tested functionally at reduced scale, and is based on mature solid-state-laser technology. Most of the parameter values that we used are being verifiedmore » by experiments now in progress. Future experiments will address the few issues that remain. As a consequence, the economic and technical risk of our DPSSL driver concept is becoming rather low. Baseline performance at 1 GW{sub e} using a new gain medium [Yb{sup 3+}-doped Sr{sub 5}(PO{sub 4}){sub 3}F or Yb:S-FAP] includes a product of laser efficiency and target gain of {eta}G = 7, and a COE of 8.6 cents/kW{center_dot}h, although values of {eta}G {ge} 11 and COEs {le}6.6 cents/kW{center_dot}h are possible at double the assumed target gain of 76 at 3.7 MJ. We present a summary of our results, discuss why other more-common types of laser media do not perform as well as Yb:S-FAP, and present a simple model that shows where DPSSL development should proceed to reduce projected COEs.« less

Fusion Breeding for Sustainable, Mid Century, Carbon Free Power

NASA Astrophysics Data System (ADS)

Manheimer, Wallace

2015-11-01

If ITER achieves Q ~10, it is still very far from useful fusion. The fusion power, and the driver power will allow only a small amount of power to be delivered, <~50MW for an ITER scale tokamak. It is unlikely, considering ``conservative design rules'' that tokamaks can ever be economical pure fusion power producers. Considering the status of other magnetic fusion concepts, it is also very unlikely that any alternate concept will either. Laser fusion does not seem to be constrained by any conservative design rules, but considering the failure of NIF to achhieve ignition, at this point it has many more obstacles to overcome than magnetic fusion. One way out of this dilemma is to use an ITER size tokamak, or a NIF size laser, as a fuel breeder for searate nuclear reactors. Hence ITER and NIF become ends in themselves, instead of steps to who knows what DEMO decades later. Such a tokamak can easily live within the consrtaints of conservative design rules. This has led the author to propose ``The Energy Park'' a sustainable, carbon free, economical, and environmently viable power source without prolifertion risk. It is one fusion breeder fuels 5 conventional nuclear reactors, and one fast neutron reactor burns the actinide wastes.

Scalloped Hibachi and Vacuum-Pressure Foil for Electra: Electron Beam Pumped KrF Laser

DTIC Science & Technology

2007-06-01

confinement fusion energy (IFE) applications [1-8]. The foils are a critical part of this durability and efficiency. The electron beam, generated in a high...and A. W. Maschke, “Design descriptions of the Prometheus- L and -H inertial fusion energy drivers,” Fusion Engineering and Design, vol. 25, pp...inertial fusion energy ,” Fusion Engineering and Design, vol. 44, pp. 371-375, March 1999. [4] I. Okuda, e. Takahashi, and Y. Owadano, “A

People counting and re-identification using fusion of video camera and laser scanner

NASA Astrophysics Data System (ADS)

Ling, Bo; Olivera, Santiago; Wagley, Raj

2016-05-01

We present a system for people counting and re-identification. It can be used by transit and homeland security agencies. Under FTA SBIR program, we have developed a preliminary system for transit passenger counting and re-identification using a laser scanner and video camera. The laser scanner is used to identify the locations of passenger's head and shoulder in an image, a challenging task in crowed environment. It can also estimate the passenger height without prior calibration. Various color models have been applied to form color signatures. Finally, using a statistical fusion and classification scheme, passengers are counted and re-identified.

Method for producing small hollow spheres

DOEpatents

Hendricks, C.D.

1979-01-09

Method is disclosed for producing small hollow spheres of glass, metal or plastic, wherein the sphere material is mixed with or contains as part of the composition a blowing agent which decomposes at high temperature (T [approx gt] 600 C). As the temperature is quickly raised, the blowing agent decomposes and the resulting gas expands from within, thus forming a hollow sphere of controllable thickness. The thus produced hollow spheres (20 to 10[sup 3] [mu]m) have a variety of application, and are particularly useful in the fabrication of targets for laser implosion such as neutron sources, laser fusion physics studies, and laser initiated fusion power plants. 1 fig.

Method and apparatus for producing small hollow spheres

DOEpatents

Hendricks, Charles D.

1979-01-01

Method and apparatus for producing small hollow spheres of glass, metal or plastic, wherein the sphere material is mixed with or contains as part of the composition a blowing agent which decomposes at high temperature (T.gtoreq.600.degree. C.). As the temperature is quickly raised, the blowing agent decomposes and the resulting gas expands from within, thus forming a hollow sphere of controllable thickness. The thus produced hollow spheres (20 to 10.sup.3 .mu.m) have a variety of application, and are particularly useful in the fabrication of targets for laser implosion such as neutron sources, laser fusion physics studies, and laser initiated fusion power plants.

Method for producing small hollow spheres

DOEpatents

Hendricks, Charles D. [Livermore, CA

1979-01-09

Method for producing small hollow spheres of glass, metal or plastic, wherein the sphere material is mixed with or contains as part of the composition a blowing agent which decomposes at high temperature (T .gtorsim. 600.degree. C). As the temperature is quickly raised, the blowing agent decomposes and the resulting gas expands from within, thus forming a hollow sphere of controllable thickness. The thus produced hollow spheres (20 to 10.sup.3 .mu.m) have a variety of application, and are particularly useful in the fabrication of targets for laser implosion such as neutron sources, laser fusion physics studies, and laser initiated fusion power plants.

Preface

NASA Astrophysics Data System (ADS)

Gauthier, Jean-Claude; Hammel, Bruce; Azechi, Hiroshi; Labaune, Christine

2006-06-01

The Fourth International Conference on Inertial Fusion Sciences and Applications (IFSA 2005) was held September 4-9, 2005 at the Bellevue Conference Center in Biarritz, France. The host organizations for this conference were the University of Bordeaux 1, the Centre National de la Recherche Scientifique (CNRS) and the Commissariat a l'Energie Atomique (CEA). The conference objective was to review of the state of the art of research in inertial fusion sciences and applications since the last conference held in Monterey California, USA, in 2003. Altogether 509 abstracts were submitted, 418 accepted, and more than 440 persons from 23 countries attended the conference. These Proceedings contain 249 of the papers presented at IFSA 2005. This collection of papers represents the manuscripts submitted to and passing the peer review process. The IFSA 2005 conference is the first of a new series of three conferences to be organized in France, Japan and the USA and governed under Annex I of the Memorandum of Agreement, signed in June 2004, among the Lawrence Livermore Laboratory operated by the University of California (UC), Osaka University, and Institut Lasers et Plasmas (ILP), operated by CNRS Delegation Aquitaine. The IFSA 2005 continued the strong tradition of the three previous conferences in Bordeaux, Kyoto and Monterey. It was the largest IFSA yet with a substantial participation from countries such as China and Russia. With a goal of achieving inertial fusion ignition and burn propagation in the laboratory, there continues to be significant progress in the international inertial fusion community. At IFSA 2005, researchers presented the exciting advances in traditional hot spot ignition approach, including results from the early experiments from the NIF laser. A particularly emphasis of the meeting was the rapid and exciting progress in the fast ignition scheme. Integrated and basic physics experiments on GekkoXII, Vulcan, and other laser-matter interaction facilities have shown promising results. A lot of new results of experiments and numerical simulations in ultra-intense laser interactions have also been presented. The Megajoule Laser (LMJ), as one of two facilities being built to achieve target ignition, was a key attraction of IFSA 2005. About 200 participants toured the LMJ construction site and the LIL laser prototype during the conference. Before the tour, a special Facility Focus session examined progress on inertial fusion facilities around the world, including the soon-to-be-completed OMEGA-EP upgrade at Rochester, USA, and FIREX I, at Osaka, Japan. Recent progresses in hohlraum physics continue to give confidence in the ultimate achievement of ignition on the NIF Laser and the Megajoule Laser. The USA are pursuing a very focused program on ICF under the National Ignition Campaign (NIC). In China, a national project has been launched, the goal of which is fusion ignition and plasma burning in about 2020. Progress in direct drive has been notable over the past few years with the cryogenic implosions at LLE, polar direct-drive that may enable to switch rapidly from an indirect- to a direct-drive laser configuration, adiabat shaping of laser pulses, and even "Saturn targets", a short circuit topic from ICF to laboratory astrophysics. About this last topic, radiative shocks and plasma jets were among the most studied subjects. There were also sessions on the technologies of al1 types of drivers, including KrF and DPSSL lasers, particle beams, and Z-pinches. Advances in Z-pinch included double-hohlraum irradiation symmetry and the construction of a PW laser beam for the Z-facility. Advance in plasma diagnostics were dominated by proton imaging from ultra-intense interactions and precise imaging spectroscopy of core implosions. Of special interest, advanced target physics and reactor design studies have started to be more present during this IFSA edition. These Proceedings start with special chapters on the keynote speeches and the Teller lectures. The keynotes give an overview of progress in inertial fusion in North America, Europe and Asia. The Teller lectures show the contributions of this year's two winners: Joe Kilkenny of General Atomics and Max Tabak of LLNL. The remainder of the Proceedings is divided into three parts. Part A covers the physics of inertial fusion; Part B covers facilities, lasers, particle beams, Z-pinches, target fabrication and reactor design; Part C covers fundamental high-energy density science and other applications of inertial fusion VI technology such as plasma diagnostics, atomic physics and X-ray sources, laboratory astrophysics and laser particle acceleration. The readers should be aware that for some of the papers, only a short version is presented in this book: the extended version will be published in a topical issue of the European Physical Journal. The IFSA International Organizing Committee and Scientific Advisory Board appreciate the efforts of inertial fusion researchers worldwide in making IFSA 2005 an extremely successful conference. Jean-Claude Gauthier, technical committee co-chair Bruce Hammel, technical committee co-chair Hiroshi Azechi, technical committee co-chair Christine Labaune, proceedings co-editor

A new gated x-ray detector for the Orion laser facility

NASA Astrophysics Data System (ADS)

Clark, David D.; Aragonez, Robert; Archuleta, Thomas; Fatherley, Valerie; Hsu, Albert; Jorgenson, Justin; Mares, Danielle; Oertel, John; Oades, Kevin; Kemshall, Paul; Thomas, Phillip; Young, Trevor; Pederson, Neal

2012-10-01

Gated X-Ray Detectors (GXD) are considered the work-horse target diagnostic of the laser based inertial confinement fusion (ICF) program. Recently, Los Alamos National Laboratory (LANL) has constructed three new GXDs for the Orion laser facility at the Atomic Weapons Establishment (AWE) in the United Kingdom. What sets these three new instruments apart from what has previously been constructed for the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory (LLNL) is: improvements in detector head microwave transmission lines, solid state embedded hard drive and updated control software, and lighter air box design and other incremental mechanical improvements. In this paper we will present the latest GXD design enhancements and sample calibration data taken on the Trident laser facility at Los Alamos National Laboratory using the newly constructed instruments.

Laser and Optical Fiber Metrology in Romania

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sporea, Dan; Sporea, Adelina

2008-04-15

The Romanian government established in the last five years a National Program for the improvement of country's infrastructure of metrology. The set goal was to develop and accredit testing and calibration laboratories, as well as certification bodies, according to the ISO 17025:2005 norm. Our Institute benefited from this policy, and developed a laboratory for laser and optical fibers metrology in order to provide testing and calibration services for the certification of laser-based industrial, medical and communication products. The paper will present the laboratory accredited facilities and some of the results obtained in the evaluation of irradiation effects of optical andmore » optoelectronic parts, tests run under the EU's Fusion Program.« less

LDRD Final Report 15-ERD-037 Matthews

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matthews, Manyalibo J.

2017-10-26

The physics and materials science involved in laser materials processing of metals was studied experimentally using custom-built test beds and in situ diagnostics. Special attention was given to laser-based powder bed fusion additive manufacturing processes, a technology critically important to the stockpile stewardship program in NNSA. New light has been shed on several phenomena such as laser-driven spatter, material displacement and morphology changes. The results presented here and in publications generated by this work have proven impactful and useful to both internal and external communities. New directions in additive manufacturing research at LLNL have been enabled, along with new scientificmore » capabilities that can serve future program needs.« less

Hollow screw-like drill in plasma using an intense Laguerre-Gaussian laser

NASA Astrophysics Data System (ADS)

Wang, Wenpeng; Shen, Baifei; Zhang, Xiaomei; Zhang, Lingang; Shi, Yin; Xu, Zhizhan

2015-02-01

With the development of ultra-intense laser technology, MeV ions can be obtained from laser-foil interactions in the laboratory. These energetic ion beams can be applied in fast ignition for inertial confinement fusion, medical therapy, and proton imaging. However, these ions are mainly accelerated in the laser propagation direction. Ion acceleration in an azimuthal orientation was scarcely studied. In this research, a doughnut Laguerre-Gaussian (LG) laser is used for the first time to examine laser-plasma interaction in the relativistic intensity regime in three-dimensional particle-in-cell simulations. Studies have shown that a novel rotation of the plasma is produced from the hollow screw-like drill of an mode laser. The angular momentum of particles in the longitudinal direction produced by the LG laser is enhanced compared with that produced by the usual laser pulses, such as linearly and circularly polarized Gaussian pulses. Moreover, the particles (including electrons and ions) can be trapped and uniformly compressed in the dark central minimum of the doughnut LG pulse. The hollow-structured LG laser has potential applications in the generation of x-rays with orbital angular momentum, plasma accelerators, fast ignition for inertial confinement fusion, and pulsars in the astrophysical environment.

Hollow screw-like drill in plasma using an intense Laguerre-Gaussian laser.

PubMed

Wang, Wenpeng; Shen, Baifei; Zhang, Xiaomei; Zhang, Lingang; Shi, Yin; Xu, Zhizhan

2015-02-05

With the development of ultra-intense laser technology, MeV ions can be obtained from laser-foil interactions in the laboratory. These energetic ion beams can be applied in fast ignition for inertial confinement fusion, medical therapy, and proton imaging. However, these ions are mainly accelerated in the laser propagation direction. Ion acceleration in an azimuthal orientation was scarcely studied. In this research, a doughnut Laguerre-Gaussian (LG) laser is used for the first time to examine laser-plasma interaction in the relativistic intensity regime in three-dimensional particle-in-cell simulations. Studies have shown that a novel rotation of the plasma is produced from the hollow screw-like drill of an mode laser. The angular momentum of particles in the longitudinal direction produced by the LG laser is enhanced compared with that produced by the usual laser pulses, such as linearly and circularly polarized Gaussian pulses. Moreover, the particles (including electrons and ions) can be trapped and uniformly compressed in the dark central minimum of the doughnut LG pulse. The hollow-structured LG laser has potential applications in the generation of x-rays with orbital angular momentum, plasma accelerators, fast ignition for inertial confinement fusion, and pulsars in the astrophysical environment.

In-situ characterization of laser-powder interaction and cooling rates through high-speed imaging of powder bed fusion additive manufacturing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scipioni Bertoli, Umberto; Guss, Gabe; Wu, Sheldon

We report detailed understanding of the complex melt pool physics plays a vital role in predicting optimal processing regimes in laser powder bed fusion additive manufacturing. In this work, we use high framerate video recording of Selective Laser Melting (SLM) to provide useful insight on the laser-powder interaction and melt pool evolution of 316 L powder layers, while also serving as a novel instrument to quantify cooling rates of the melt pool. The experiment was performed using two powder types – one gas- and one water-atomized – to further clarify how morphological and chemical differences between these two feedstock materialsmore » influence the laser melting process. Finally, experimentally determined cooling rates are compared with values obtained through computer simulation, and the relationship between cooling rate and grain cell size is compared with data previously published in the literature.« less

Inertial Confinement Fusion Quarterly Report: April--June 1993. Volume 3, Number 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacGowan, B.J.; Kotowski, M.; Schleich, D.

1993-11-01

This issue of the ICF Quarterly contains six articles describing recent advances in Lawrence Livermore National Laboratory`s inertial confinement fusion (ICF) program. The current emphasis of the ICF program is in support of DOE`s National Ignition Facility (NIF) initiative for demonstrating ignition and gain with a 1-2 MJ glass laser. The articles describe recent Nova experiments and investigations tailored towards enhancing understanding of the key physics and technological issues for the NIF. Titles of the articles are: development of large-aperture KDP crystals; inner-shell photo-ionized X-ray lasers; X-ray radiographic measurements of radiation-driven shock and interface motion in solid density materials; themore » role of nodule defects in laser-induced damage of multilayer optical coatings; techniques for Mbar to near-Gbar equation-of-state measurements with the Nova laser; parametric instabilities and laser-beam smoothing.« less

Laser ablation under different electron heat conduction models in inertial confinement fusion

NASA Astrophysics Data System (ADS)

Li, Shuanggui; Ren, Guoli; Huo, Wen Yi

2018-06-01

In this paper, we study the influence of three different electron heat conduction models on the laser ablation of gold plane target. Different from previous studies, we concentrate on the plasma conditions, the conversion efficiency from laser into soft x rays and the scaling relation of mass ablation, which are relevant to hohlraum physics study in indirect drive inertial confinement fusion. We find that the simulated electron temperature in corona region is sensitive to the electron heat conduction models. For different electron heat conduction models, there are obvious differences in magnitude and spatial profile of electron temperature. For the flux limit model, the calculated conversion efficiency is sensitive to flux limiters. In the laser ablation of gold, most of the laser energies are converted into x rays. So the scaling relation of mass ablation rate is quite different from that of low Z materials.

Using Laser Ultrasound to Detect Subsurface Defects in Metal Laser Powder Bed Fusion Components

NASA Astrophysics Data System (ADS)

Everton, Sarah; Dickens, Phill; Tuck, Chris; Dutton, Ben

2018-03-01

Laser powder bed fusion offers many advantages over conventional manufacturing methods, such as the integration of multiple parts that can result in significant weight-savings. The increased design freedom that layer-wise manufacture allows has also been seen to enhance component performance at little or no added cost. For such benefits to be realized, however, the material quality must first be assured. Laser ultrasonic testing is a noncontact inspection technique that has been proposed as suitable for in situ monitoring of metal additive manufacturing processes. This article explores the current capability of this technique to detect manufactured, subsurface defects in Ti-6Al-4V samples, ex situ. The results are compared with x-ray computed tomography reconstructions and focus variation microscopy. Although laser ultrasound has been used to identify material discontinuities, further work is required before this technique could be implemented in situ.

Experimental comparison of photogrammetry for additive manufactured parts with and without laser speckle projection

NASA Astrophysics Data System (ADS)

Sims-Waterhouse, D.; Bointon, P.; Piano, S.; Leach, R. K.

2017-06-01

In this paper we show that, by using a photogrammetry system with and without laser speckle, a large range of additive manufacturing (AM) parts with different geometries, materials and post-processing textures can be measured to high accuracy. AM test artefacts have been produced in three materials: polymer powder bed fusion (nylon-12), metal powder bed fusion (Ti-6Al-4V) and polymer material extrusion (ABS plastic). Each test artefact was then measured with the photogrammetry system in both normal and laser speckle projection modes and the resulting point clouds compared with the artefact CAD model. The results show that laser speckle projection can result in a reduction of the point cloud standard deviation from the CAD data of up to 101 μm. A complex relationship with surface texture, artefact geometry and the laser speckle projection is also observed and discussed.

In-situ characterization of laser-powder interaction and cooling rates through high-speed imaging of powder bed fusion additive manufacturing

DOE PAGES

Scipioni Bertoli, Umberto; Guss, Gabe; Wu, Sheldon; ...

2017-09-21

We report detailed understanding of the complex melt pool physics plays a vital role in predicting optimal processing regimes in laser powder bed fusion additive manufacturing. In this work, we use high framerate video recording of Selective Laser Melting (SLM) to provide useful insight on the laser-powder interaction and melt pool evolution of 316 L powder layers, while also serving as a novel instrument to quantify cooling rates of the melt pool. The experiment was performed using two powder types – one gas- and one water-atomized – to further clarify how morphological and chemical differences between these two feedstock materialsmore » influence the laser melting process. Finally, experimentally determined cooling rates are compared with values obtained through computer simulation, and the relationship between cooling rate and grain cell size is compared with data previously published in the literature.« less

Direct Heating of a Laser-Imploded Core by Ultraintense Laser-Driven Ions

NASA Astrophysics Data System (ADS)

Kitagawa, Y.; Mori, Y.; Komeda, O.; Ishii, K.; Hanayama, R.; Fujita, K.; Okihara, S.; Sekine, T.; Satoh, N.; Kurita, T.; Takagi, M.; Watari, T.; Kawashima, T.; Kan, H.; Nishimura, Y.; Sunahara, A.; Sentoku, Y.; Nakamura, N.; Kondo, T.; Fujine, M.; Azuma, H.; Motohiro, T.; Hioki, T.; Kakeno, M.; Miura, E.; Arikawa, Y.; Nagai, T.; Abe, Y.; Ozaki, S.; Noda, A.

2015-05-01

A novel direct core heating fusion process is introduced, in which a preimploded core is predominantly heated by energetic ions driven by LFEX, an extremely energetic ultrashort pulse laser. Consequently, we have observed the D (d ,n )He 3 -reacted neutrons (DD beam-fusion neutrons) with the yield of 5 ×108 n /4 π sr . Examination of the beam-fusion neutrons verified that the ions directly collide with the core plasma. While the hot electrons heat the whole core volume, the energetic ions deposit their energies locally in the core, forming hot spots for fuel ignition. As evidenced in the spectrum, the process simultaneously excited thermal neutrons with the yield of 6 ×107 n /4 π sr , raising the local core temperature from 0.8 to 1.8 keV. A one-dimensional hydrocode STAR 1D explains the shell implosion dynamics including the beam fusion and thermal fusion initiated by fast deuterons and carbon ions. A two-dimensional collisional particle-in-cell code predicts the core heating due to resistive processes driven by hot electrons, and also the generation of fast ions, which could be an additional heating source when they reach the core. Since the core density is limited to 2 g /cm3 in the current experiment, neither hot electrons nor fast ions can efficiently deposit their energy and the neutron yield remains low. In future work, we will achieve the higher core density (>10 g /cm3 ); then hot electrons could contribute more to the core heating via drag heating. Together with hot electrons, the ion contribution to fast ignition is indispensable for realizing high-gain fusion. By virtue of its core heating and ignition, the proposed scheme can potentially achieve high gain fusion.

Direct heating of a laser-imploded core by ultraintense laser-driven ions.

PubMed

Kitagawa, Y; Mori, Y; Komeda, O; Ishii, K; Hanayama, R; Fujita, K; Okihara, S; Sekine, T; Satoh, N; Kurita, T; Takagi, M; Watari, T; Kawashima, T; Kan, H; Nishimura, Y; Sunahara, A; Sentoku, Y; Nakamura, N; Kondo, T; Fujine, M; Azuma, H; Motohiro, T; Hioki, T; Kakeno, M; Miura, E; Arikawa, Y; Nagai, T; Abe, Y; Ozaki, S; Noda, A

2015-05-15

A novel direct core heating fusion process is introduced, in which a preimploded core is predominantly heated by energetic ions driven by LFEX, an extremely energetic ultrashort pulse laser. Consequently, we have observed the D(d,n)^{3}He-reacted neutrons (DD beam-fusion neutrons) with the yield of 5×10^{8} n/4π sr. Examination of the beam-fusion neutrons verified that the ions directly collide with the core plasma. While the hot electrons heat the whole core volume, the energetic ions deposit their energies locally in the core, forming hot spots for fuel ignition. As evidenced in the spectrum, the process simultaneously excited thermal neutrons with the yield of 6×10^{7} n/4π sr, raising the local core temperature from 0.8 to 1.8 keV. A one-dimensional hydrocode STAR 1D explains the shell implosion dynamics including the beam fusion and thermal fusion initiated by fast deuterons and carbon ions. A two-dimensional collisional particle-in-cell code predicts the core heating due to resistive processes driven by hot electrons, and also the generation of fast ions, which could be an additional heating source when they reach the core. Since the core density is limited to 2 g/cm^{3} in the current experiment, neither hot electrons nor fast ions can efficiently deposit their energy and the neutron yield remains low. In future work, we will achieve the higher core density (>10 g/cm^{3}); then hot electrons could contribute more to the core heating via drag heating. Together with hot electrons, the ion contribution to fast ignition is indispensable for realizing high-gain fusion. By virtue of its core heating and ignition, the proposed scheme can potentially achieve high gain fusion.

Development of a cryogenically cooled platform for the Magnetized Liner Inertial Fusion (MagLIF) Program [Development of a cryogenically-cooled platform for the Magnetized Liner Inertial Fusion (MagLIF) Concept

DOE PAGES

Awe, T. J.; Shelton, K. P.; Sefkow, A. B.; ...

2017-09-25

A cryogenically cooled hardware platform has been developed and commissioned on the Z Facility at Sandia National Laboratories in support of the Magnetized Liner Inertial Fusion (MagLIF) Program. MagLIF is a magneto-inertial fusion concept that employs a magnetically imploded metallic tube (liner) to compress and inertially confine premagnetized and preheated fusion fuel. The fuel is preheated using a ~2 kJ laser that must pass through a ~1.5-3.5-μm-thick polyimide “window” at the target’s laser entrance hole (LEH). As the terawatt-class laser interacts with the dense window, laser plasma instabilities (LPIs) can develop, which reduce the preheat energy delivered to the fuel,more » initiate fuel contamination, and degrade target performance. Cryogenically cooled targets increase the parameter space accessible to MagLIF target designs by allowing nearly 10 times thinner windows to be used for any accessible gas density. Thinner LEH windows reduce the deleterious effects of difficult to model LPIs. The Z Facility’s cryogenic infrastructure has been significantly altered to enable compatibility with the premagnetization and fuel preheat stages of MagLIF. The MagLIF cryostat brings the liquid helium coolant directly to the target via an electrically resistive conduit. This design maximizes cooling power while allowing rapid diffusion of the axial magnetic field supplied by external Helmholtz-like coils. A variety of techniques have been developed to mitigate the accumulation of ice from vacuum chamber contaminants on the cooled LEH window, as even a few hundred nanometers of ice would impact laser energy coupling to the fuel region. Here, the MagLIF cryostat has demonstrated compatibility with the premagnetization and preheat stages of MagLIF and the ability to cool targets to liquid deuterium temperatures in approximately 5 min.« less

Development of a cryogenically cooled platform for the Magnetized Liner Inertial Fusion (MagLIF) Program [Development of a cryogenically-cooled platform for the Magnetized Liner Inertial Fusion (MagLIF) Concept

DOE Office of Scientific and Technical Information (OSTI.GOV)

Awe, T. J.; Shelton, K. P.; Sefkow, A. B.

A cryogenically cooled hardware platform has been developed and commissioned on the Z Facility at Sandia National Laboratories in support of the Magnetized Liner Inertial Fusion (MagLIF) Program. MagLIF is a magneto-inertial fusion concept that employs a magnetically imploded metallic tube (liner) to compress and inertially confine premagnetized and preheated fusion fuel. The fuel is preheated using a ~2 kJ laser that must pass through a ~1.5-3.5-μm-thick polyimide “window” at the target’s laser entrance hole (LEH). As the terawatt-class laser interacts with the dense window, laser plasma instabilities (LPIs) can develop, which reduce the preheat energy delivered to the fuel,more » initiate fuel contamination, and degrade target performance. Cryogenically cooled targets increase the parameter space accessible to MagLIF target designs by allowing nearly 10 times thinner windows to be used for any accessible gas density. Thinner LEH windows reduce the deleterious effects of difficult to model LPIs. The Z Facility’s cryogenic infrastructure has been significantly altered to enable compatibility with the premagnetization and fuel preheat stages of MagLIF. The MagLIF cryostat brings the liquid helium coolant directly to the target via an electrically resistive conduit. This design maximizes cooling power while allowing rapid diffusion of the axial magnetic field supplied by external Helmholtz-like coils. A variety of techniques have been developed to mitigate the accumulation of ice from vacuum chamber contaminants on the cooled LEH window, as even a few hundred nanometers of ice would impact laser energy coupling to the fuel region. Here, the MagLIF cryostat has demonstrated compatibility with the premagnetization and preheat stages of MagLIF and the ability to cool targets to liquid deuterium temperatures in approximately 5 min.« less

Plasma photonics in ICF & HED conditions

NASA Astrophysics Data System (ADS)

Michel, Pierre; Turnbull, David; Divol, Laurent; Pollock, Bradley; Chen, Cecilia Y.; Tubman, Eleanor; Goyon, Clement S.; Moody, John D.

2015-11-01

Interactions between multiple high-energy laser beams and plasma can be used to imprint refractive micro-structures in plasmas via the lasers' ponderomotive force. For example, Inertial confinement fusion (ICF) experiments at the National Ignition Facility already rely on the use of plasma gratings to redirect laser light inside an ICF target and tune the symmetry of the imploded core. More recently, we proposed new concepts of plasma polarizer and waveplate, based on two-wave mixing schemes and laser-induced plasma birefringence. In this talk, we will present new experimental results showing the first demonstration of a fully tunable plasma waveplate, which achieved near-perfect circular laser polarization. We will discuss further prospects for novel ``plasma photonics'' concepts based on two- and four-wave mixing, such as optical switches, bandpass filters, anti-reflection blockers etc. These might find applications in ICF and HED experiments by allowing to manipulate the lasers directly in-situ (i.e. inside the targets), as well as for the design of high power laser systems. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

A tesselation-based model for intensity estimation and laser plasma interactions calculations in three dimensions

NASA Astrophysics Data System (ADS)

Colaïtis, A.; Chapman, T.; Strozzi, D.; Divol, L.; Michel, P.

2018-03-01

A three-dimensional laser propagation model for computation of laser-plasma interactions is presented. It is focused on indirect drive geometries in inertial confinement fusion and formulated for use at large temporal and spatial scales. A modified tesselation-based estimator and a relaxation scheme are used to estimate the intensity distribution in plasma from geometrical optics rays. Comparisons with reference solutions show that this approach is well-suited to reproduce realistic 3D intensity field distributions of beams smoothed by phase plates. It is shown that the method requires a reduced number of rays compared to traditional rigid-scale intensity estimation. Using this field estimator, we have implemented laser refraction, inverse-bremsstrahlung absorption, and steady-state crossed-beam energy transfer with a linear kinetic model in the numerical code Vampire. Probe beam amplification and laser spot shapes are compared with experimental results and pf3d paraxial simulations. These results are promising for the efficient and accurate computation of laser intensity distributions in holhraums, which is of importance for determining the capsule implosion shape and risks of laser-plasma instabilities such as hot electron generation and backscatter in multi-beam configurations.

Fusion Reactions and Matter-Antimatter Annihilation for Space Propulsion

DTIC Science & Technology

2005-07-13

shielding. λ D-3He eliminates the need for a complicated tritium-breeding blanked and tritium-processing system. 4 - MAGNETIC FUSION ENERGY (MFE...resulting specific powers. 5 - INERTIAL FUSION ENERGY (IFE) The possibility of igniting thermonuclear micro-explosions with pulsed laser beams was... fusion energy to antimatter rest mass energy, β, of 1.6 × 107. However, energy utilization is also lower due to the isotropic expansion process (ηe ~ 15

A reflective hydrogen sensor based on fiber ring laser with PCF modal interferometer

NASA Astrophysics Data System (ADS)

Zhang, Ya-Nan; Zhang, Aozhuo; Han, Bo; E, Siyu

2018-06-01

A new hydrogen sensor based on a fiber ring laser with a photonic crystal fiber (PCF) modal interferometer is proposed. The reflective PCF modal interferometer, which is fabricated by forming two collapse regions on the two ends of PCF with a fusion discharge technique, is utilized as the sensing head and filter. Particularly, the Pd/WO3 hydrogen-sensitive thin film is coated on the PCF for hydrogen sensing. The combination of the fiber ring laser and PCF modal interferometer gives the sensor a high signal-to-noise ratio and an improved detection limit. Experimental results show that the sensing system can achieve a hydrogen sensitivity of 1.28 nm/%, a high signal-to-noise ratio (∼30 dB), a narrow full width at half maximum (∼0.05 nm), and low detection limit of 0.0133%.

Comparison of the recently proposed super-Marx generator approach to thermonuclear ignition with the deuterium-tritium laser fusion-fission hybrid concept by the Lawrence Livermore National Laboratory

DOE PAGES

Winterberg, F.

2009-01-01

The recently proposed super-Marx generator pure deuterium microdetonation ignition concept is compared to the Lawrence Livermore National Ignition Facility (NIF) Laser deuterium-tritium fusion-fission hybrid concept (LIFE). In a super-Marx generator, a large number of ordinary Marx generators charge up a much larger second stage ultrahigh voltage Marx generator from which for the ignition of a pure deuterium microexplosion an intense GeV ion beam can be extracted. Typical examples of the LIFE concept are a fusion gain of 30 and a fission gain of 10, making up a total gain of 300, with about ten times more energy released into fissionmore » as compared to fusion. This means the substantial release of fission products, as in fissionless pure fission reactors. In the super-Marx approach for the ignition of pure deuterium microdetonation, a gain of the same magnitude can, in theory, be reached. If feasible, the super-Marx generator deuterium ignition approach would make lasers obsolete as a means for the ignition of thermonuclear microexplosions.« less

Origins and Scaling of Hot-Electron Preheat in Ignition-Scale Direct-Drive Inertial Confinement Fusion Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rosenberg, M. J.; Solodov, A. A.; Myatt, J. F.

Planar laser-plasma interaction (LPI) experiments at the National Ignition Facility (NIF) have allowed access for the rst time to regimes of electron density scale length (~500 to 700 μm), electron temperature (~3 to 5 keV), and laser intensity (6 to 16 x 10 14 W/cm 2) that are relevant to direct-drive inertial confinement fusion ignition. Unlike in shorter-scale-length plasmas on OMEGA, scattered-light data on the NIF show that the near-quarter-critical LPI physics is dominated by stimulated Raman scattering (SRS) rather than by two-plasmon decay (TPD). This difference in regime is explained based on absolute SRS and TPD threshold considerations. SRSmore » sidescatter tangential to density contours and other SRS mechanisms are observed. The fraction of laser energy converted to hot electrons is ~0.7% to 2.9%, consistent with observed levels of SRS. The intensity threshold for hot-electron production is assessed, and the use of a Si ablator slightly increases this threshold from ~4 x 10 14 to ~6 x 10 14 W/cm 2. These results have significant implications for mitigation of LPI hot-electron preheat in direct-drive ignition designs.« less

Origins and Scaling of Hot-Electron Preheat in Ignition-Scale Direct-Drive Inertial Confinement Fusion Experiments

DOE PAGES

Rosenberg, M. J.; Solodov, A. A.; Myatt, J. F.; ...

2018-01-29

Planar laser-plasma interaction (LPI) experiments at the National Ignition Facility (NIF) have allowed access for the rst time to regimes of electron density scale length (~500 to 700 μm), electron temperature (~3 to 5 keV), and laser intensity (6 to 16 x 10 14 W/cm 2) that are relevant to direct-drive inertial confinement fusion ignition. Unlike in shorter-scale-length plasmas on OMEGA, scattered-light data on the NIF show that the near-quarter-critical LPI physics is dominated by stimulated Raman scattering (SRS) rather than by two-plasmon decay (TPD). This difference in regime is explained based on absolute SRS and TPD threshold considerations. SRSmore » sidescatter tangential to density contours and other SRS mechanisms are observed. The fraction of laser energy converted to hot electrons is ~0.7% to 2.9%, consistent with observed levels of SRS. The intensity threshold for hot-electron production is assessed, and the use of a Si ablator slightly increases this threshold from ~4 x 10 14 to ~6 x 10 14 W/cm 2. These results have significant implications for mitigation of LPI hot-electron preheat in direct-drive ignition designs.« less

Origins and Scaling of Hot-Electron Preheat in Ignition-Scale Direct-Drive Inertial Confinement Fusion Experiments

NASA Astrophysics Data System (ADS)

Rosenberg, M. J.; Solodov, A. A.; Myatt, J. F.; Seka, W.; Michel, P.; Hohenberger, M.; Short, R. W.; Epstein, R.; Regan, S. P.; Campbell, E. M.; Chapman, T.; Goyon, C.; Ralph, J. E.; Barrios, M. A.; Moody, J. D.; Bates, J. W.

2018-01-01

Planar laser-plasma interaction (LPI) experiments at the National Ignition Facility (NIF) have allowed access for the first time to regimes of electron density scale length (˜500 to 700 μ m ), electron temperature (˜3 to 5 keV), and laser intensity (6 to 16 ×1014 W /cm2 ) that are relevant to direct-drive inertial confinement fusion ignition. Unlike in shorter-scale-length plasmas on OMEGA, scattered-light data on the NIF show that the near-quarter-critical LPI physics is dominated by stimulated Raman scattering (SRS) rather than by two-plasmon decay (TPD). This difference in regime is explained based on absolute SRS and TPD threshold considerations. SRS sidescatter tangential to density contours and other SRS mechanisms are observed. The fraction of laser energy converted to hot electrons is ˜0.7 % to 2.9%, consistent with observed levels of SRS. The intensity threshold for hot-electron production is assessed, and the use of a Si ablator slightly increases this threshold from ˜4×10 14 to ˜6 ×1014 W /cm2 . These results have significant implications for mitigation of LPI hot-electron preheat in direct-drive ignition designs.

Phase structures and morphologies of tempered CA6NM stainless steel welded by hybrid laser-arc process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mirakhorli, F., E-mail: Fatemeh.mirakhorli.1@ens.e

The post-weld tempered microstructure of hybrid laser-arc welded CA6NM, a cast low carbon martensitic stainless steel, was investigated. The microstructural evolutions from the fusion zone to the base metal were characterized in detail using optical microscopy, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD) and microhardness techniques. The fusion zone, in its post-weld tempered condition, consisted of tempered lath martensite, residual delta-ferrite with various morphologies, reversed austenite and chromium carbides. The reversed austenite, which can be detected through both EBSD and XRD techniques, was found to be finely dispersed along the martensite lath boundaries, particularly at triplemore » junctions. Based on the EBSD analysis, the orientation relationship between the reversed austenite and the adjacent martensite laths seemed to follow the Kurdjumov-Sachs (K-S) model. The results also revealed the presence of the reversed austenite in the different regions of the heat affected zone after post-weld tempering. The microindentation hardness distribution was measured, and correlated to the evolution of the corresponding microstructure across the welds. - Highlights: •The EBSD analysis was performed on hybrid laser-arc welded CA6NM. •The FZ consisted of tempered lath martensite, reversed austenite, carbides and δ ferrite after tempering. •The reversed γ was formed along the α′ lath boundaries, particularly at triple junctions.« less

Laser-plasma interaction experiments and diagnostics at NRL (Naval Research Laboratory). Memorandum report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ripin, B.H.; Grun, J.; Herbst, M.J.

Laser plasma interaction experiments have now advanced to the point where very quantitative measurements are required to elucidate the physic issues important for laser fusion and other applications. Detailed time-resolved knowledge of the plasma density, temperature, velocity gradients, spatial structure, heat flow characteristics, radiation emission, etc, are needed over tremendou ranges of plasma density and temperature. Moreover, the time scales are very short, aggrevating the difficulty of the measurements further. Nonetheless, such substantial progress has been made in diagnostic development during the past few years that we are now able to do well diagnosed experiments. In this paper the authorsmore » review recent diagnostic developments for laser-plasma interactions, outline their regimes of applicability, and show examples of their utility. In addition to diagnostics for the high densities and temperature characteristic of laser fusion physics studies, diagnostics designed to study the two-stream interactions of laser created plasma flowing through an ambient low density plasma will be described.« less

Laser program annual report 1983

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hendricks, C.D.; Rufer, M.L.; Murphy, P.W.

1984-06-01

In the 1983 Laser Program Annual Report we present the accomplishments and unclassified activities of the Laser Program at Lawrence Livermore National laboratory (LLNL) for the year 1983. It should be noted that the report, of necessity, is a summary, and more detailed expositions of the research can be found in the many publications and reports authored by staff members in the Laser Program. The purpose of this report is to present our work in a brief form, but with sufficient depth to provide an overview of the analytical and experimental aspects of the LLNL Inertial-Confinement Fusion (ICF) Program. Themore » format of this report is basically the same as that of previous years. Section 1 is an overview and highlights the important accomplishments and directions of the Program. Sections 2 through 7 provide the detailed information on the various major parts of the Program: Laser Systems and Operations, Target Design, Target Fabrication, Fusion Experiments, Laser Research and Development, and Energy Applications.« less

Optical Performance Of The Gemini Carbon Dioxide Laser Fusion System

NASA Astrophysics Data System (ADS)

Viswanathan, V. K.; Hayden, J. J.; Liberman, I.

1980-11-01

The performance of the Gemini two beam carbon dioxide laser fusion system was recently upgraded by installation of optical components with improved quality in the final amplifier. A theoretical analysis was conducted in conlunction with measurements of the new performance. The analysis and experimental procedures, and results obtained are reported and compared. Good agreement was found which was within the uncertainties of the analysis and the inaccuracies of the experiments. The focal spot Strehl ratio was between 0.24 and 0.3 for both beams.

Inertial confinement fusion quarterly report, October--December 1992. Volume 3, No. 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dixit, S.N.

1992-12-31

This report contains papers on the following topics: The Beamlet Front End: Prototype of a new pulse generation system;imaging biological objects with x-ray lasers; coherent XUV generation via high-order harmonic generation in rare gases; theory of high-order harmonic generation; two-dimensional computer simulations of ultra- intense, short-pulse laser-plasma interactions; neutron detectors for measuring the fusion burn history of ICF targets; the recirculator; and lasnex evolves to exploit computer industry advances.

Method for nondestructive fuel assay of laser fusion targets

DOEpatents

Farnum, Eugene H.; Fries, R. Jay

1976-01-01

A method for nondestructively determining the deuterium and tritium content of laser fusion targets by counting the x rays produced by the interaction of tritium beta particles with the walls of the microballoons used to contain the deuterium and tritium gas mixture under high pressure. The x rays provide a direct measure of the tritium content and a means for calculating the deuterium content using the initial known D-T ratio and the known deuterium and tritium diffusion rates.

Additive Manufacturing of Single-Crystal Superalloy CMSX-4 Through Scanning Laser Epitaxy: Computational Modeling, Experimental Process Development, and Process Parameter Optimization

NASA Astrophysics Data System (ADS)

Basak, Amrita; Acharya, Ranadip; Das, Suman

2016-08-01

This paper focuses on additive manufacturing (AM) of single-crystal (SX) nickel-based superalloy CMSX-4 through scanning laser epitaxy (SLE). SLE, a powder bed fusion-based AM process was explored for the purpose of producing crack-free, dense deposits of CMSX-4 on top of similar chemistry investment-cast substrates. Optical microscopy and scanning electron microscopy (SEM) investigations revealed the presence of dendritic microstructures that consisted of fine γ' precipitates within the γ matrix in the deposit region. Computational fluid dynamics (CFD)-based process modeling, statistical design of experiments (DoE), and microstructural characterization techniques were combined to produce metallurgically bonded single-crystal deposits of more than 500 μm height in a single pass along the entire length of the substrate. A customized quantitative metallography based image analysis technique was employed for automatic extraction of various deposit quality metrics from the digital cross-sectional micrographs. The processing parameters were varied, and optimal processing windows were identified to obtain good quality deposits. The results reported here represent one of the few successes obtained in producing single-crystal epitaxial deposits through a powder bed fusion-based metal AM process and thus demonstrate the potential of SLE to repair and manufacture single-crystal hot section components of gas turbine systems from nickel-based superalloy powders.

Direct-drive inertial confinement fusion: A review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Craxton, R. S.; Anderson, K. S.; Boehly, T. R.

The direct-drive, laser-based approach to inertial confinement fusion (ICF) is reviewed from its inception following the demonstration of the first laser to its implementation on the present generation of high-power lasers. The review focuses on the evolution of scientific understanding gained from target-physics experiments in many areas, identifying problems that were demonstrated and the solutions implemented. The review starts with the basic understanding of laser–plasma interactions that was obtained before the declassification of laser-induced compression in the early 1970s and continues with the compression experiments using infrared lasers in the late 1970s that produced thermonuclear neutrons. The problem of suprathermalmore » electrons and the target preheat that they caused, associated with the infrared laser wavelength, led to lasers being built after 1980 to operate at shorter wavelengths, especially 0.35 μm—the third harmonic of the Nd:glass laser—and 0.248 μm (the KrF gas laser). The main physics areas relevant to direct drive are reviewed. The primary absorption mechanism at short wavelengths is classical inverse bremsstrahlung. Nonuniformities imprinted on the target by laser irradiation have been addressed by the development of a number of beam-smoothing techniques and imprint-mitigation strategies. The effects of hydrodynamic instabilities are mitigated by a combination of imprint reduction and target designs that minimize the instability growth rates. Several coronal plasma physics processes are reviewed. The two-plasmon–decay instability, stimulated Brillouin scattering (together with cross-beam energy transfer), and (possibly) stimulated Raman scattering are identified as potential concerns, placing constraints on the laser intensities used in target designs, while other processes (self-focusing and filamentation, the parametric decay instability, and magnetic fields), once considered important, are now of lesser concern for mainline direct-drive target concepts. Filamentation is largely suppressed by beam smoothing. Thermal transport modeling, important to the interpretation of experiments and to target design, has been found to be nonlocal in nature. Advances in shock timing and equation-of-state measurements relevant to direct-drive ICF are reported. Room-temperature implosions have provided an increased understanding of the importance of stability and uniformity. The evolution of cryogenic implosion capabilities, leading to an extensive series carried out on the 60-beam OMEGA laser [Boehly et al., Opt. Commun. 133, 495 (1997)], is reviewed together with major advances in cryogenic target formation. A polar-drive concept has been developed that will enable direct-drive–ignition experiments to be performed on the National Ignition Facility [Haynam et al., Appl. Opt. 46(16), 3276 (2007)]. The advantages offered by the alternative approaches of fast ignition and shock ignition and the issues associated with these concepts are described. The lessons learned from target-physics and implosion experiments are taken into account in ignition and high-gain target designs for laser wavelengths of 1/3 μm and 1/4 μm. Substantial advances in direct-drive inertial fusion reactor concepts are reviewed. Overall, the progress in scientific understanding over the past five decades has been enormous, to the point that inertial fusion energy using direct drive shows significant promise as a future environmentally attractive energy source.« less

Direct-drive inertial confinement fusion: A review

DOE PAGES

Craxton, R. S.; Anderson, K. S.; Boehly, T. R.; ...

2015-11-25

In this study, the direct-drive, laser-based approach to inertial confinement fusion (ICF) is reviewed from its inception following the demonstration of the first laser to its implementation on the present generation of high-power lasers. The review focuses on the evolution of scientific understanding gained from target-physics experiments in many areas, identifying problems that were demonstrated and the solutions implemented. The review starts with the basic understanding of laser–plasma interactions that was obtained before the declassification of laser-induced compression in the early 1970s and continues with the compression experiments using infrared lasers in the late 1970s that produced thermonuclear neutrons. Themore » problem of suprathermal electrons and the target preheat that they caused, associated with the infrared laser wavelength, led to lasers being built after 1980 to operate at shorter wavelengths, especially 0.35 um—the third harmonic of the Nd:glass laser—and 0.248 um (the KrF gas laser). The main physics areas relevant to direct drive are reviewed. The primary absorption mechanism at short wavelengths is classical inverse bremsstrahlung. Nonuniformities imprinted on the target by laser irradiation have been addressed by the development of a number of beam-smoothing techniques and imprint-mitigation strategies. The effects of hydrodynamic instabilities are mitigated by a combination of imprint reduction and target designs that minimize the instability growth rates. Several coronal plasma physics processes are reviewed. The two-plasmon–decay instability, stimulated Brillouin scattering (together with cross-beam energy transfer), and (possibly) stimulated Raman scattering are identified as potential concerns, placing constraints on the laser intensities used in target designs, while other processes (self-focusing and filamentation, the parametric decay instability, and magnetic fields), once considered important, are now of lesser concern for mainline direct-drive target concepts. Filamentation is largely suppressed by beam smoothing. Thermal transport modeling, important to the interpretation of experiments and to target design, has been found to be non-local in nature. Advances in shock timing and equation-of-state measurements relevant to direct-drive ICF are reported. Room-temperature implosions have provided an increased understanding of the importance of stability and uniformity. The evolution of cryogenic implosion capabilities, leading to an extensive series carried out on the 60-beam OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)], is reviewed together with major advances in cryogenic target formation. A polar-drive concept has been developed that will enable direct-drive–ignition experiments to be performed on the National Ignition Facility [C. A. Haynam et al., Appl. Opt. 46 (16), 3276 (2007)]. The advantages offered by the alternative approaches of fast ignition and shock ignition and the issues associated with these concepts are described. The lessons learned from target-physics and implosion experiments are taken into account in ignition and high-gain target designs for laser wavelengths of 1/3 μm and 1/4 μm. Substantial advances in direct-drive inertial fusion reactor concepts are reviewed. Overall, the progress in scientific understanding over the past five decades has been enormous, to the point that inertial fusion energy using direct drive shows significant promise as a future environmentally attractive energy source.« less

Direct-drive inertial confinement fusion: A review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Craxton, R. S.; Anderson, K. S.; Boehly, T. R.

In this study, the direct-drive, laser-based approach to inertial confinement fusion (ICF) is reviewed from its inception following the demonstration of the first laser to its implementation on the present generation of high-power lasers. The review focuses on the evolution of scientific understanding gained from target-physics experiments in many areas, identifying problems that were demonstrated and the solutions implemented. The review starts with the basic understanding of laser–plasma interactions that was obtained before the declassification of laser-induced compression in the early 1970s and continues with the compression experiments using infrared lasers in the late 1970s that produced thermonuclear neutrons. Themore » problem of suprathermal electrons and the target preheat that they caused, associated with the infrared laser wavelength, led to lasers being built after 1980 to operate at shorter wavelengths, especially 0.35 um—the third harmonic of the Nd:glass laser—and 0.248 um (the KrF gas laser). The main physics areas relevant to direct drive are reviewed. The primary absorption mechanism at short wavelengths is classical inverse bremsstrahlung. Nonuniformities imprinted on the target by laser irradiation have been addressed by the development of a number of beam-smoothing techniques and imprint-mitigation strategies. The effects of hydrodynamic instabilities are mitigated by a combination of imprint reduction and target designs that minimize the instability growth rates. Several coronal plasma physics processes are reviewed. The two-plasmon–decay instability, stimulated Brillouin scattering (together with cross-beam energy transfer), and (possibly) stimulated Raman scattering are identified as potential concerns, placing constraints on the laser intensities used in target designs, while other processes (self-focusing and filamentation, the parametric decay instability, and magnetic fields), once considered important, are now of lesser concern for mainline direct-drive target concepts. Filamentation is largely suppressed by beam smoothing. Thermal transport modeling, important to the interpretation of experiments and to target design, has been found to be non-local in nature. Advances in shock timing and equation-of-state measurements relevant to direct-drive ICF are reported. Room-temperature implosions have provided an increased understanding of the importance of stability and uniformity. The evolution of cryogenic implosion capabilities, leading to an extensive series carried out on the 60-beam OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)], is reviewed together with major advances in cryogenic target formation. A polar-drive concept has been developed that will enable direct-drive–ignition experiments to be performed on the National Ignition Facility [C. A. Haynam et al., Appl. Opt. 46 (16), 3276 (2007)]. The advantages offered by the alternative approaches of fast ignition and shock ignition and the issues associated with these concepts are described. The lessons learned from target-physics and implosion experiments are taken into account in ignition and high-gain target designs for laser wavelengths of 1/3 μm and 1/4 μm. Substantial advances in direct-drive inertial fusion reactor concepts are reviewed. Overall, the progress in scientific understanding over the past five decades has been enormous, to the point that inertial fusion energy using direct drive shows significant promise as a future environmentally attractive energy source.« less

Pulsed Laser Gate Experiment for Magnetized Liner Inertial Fusion (MagLIF)

NASA Astrophysics Data System (ADS)

Miller, S. M.; Slutz, S. A.; Gomez, M. R.; Klein, S. R.; Campbell, P. C.; Woolstrum, J. M.; Yager-Elorriaga, D. A.; Jordan, N. M.; Lau, Y. Y.; Gilgenbach, R. M.; McBride, R. D.

2017-10-01

Fuel preheating in full scale magnetized liner inertial fusion (MagLIF) currently has low efficiency. This loss is thought to occur from laser-plasma interactions (LPI) at the laser entrance window (LEW). The gaseous fuel is held in a pressurized vessel by the thin mylar LEW that must be removed right before heating. To ensure more laser energy heats the fuel, the LEW could be weakened at an early time. One proposed solution is to use the current from a small pulse generator to break the LEW allowing it to open outward from the fuel. With the LEW removed away from the laser path, LPI losses would be reduced. Wire attached to a 13 kV mini-pulser will be used to remove the LEW from the laser path. We will report on LEW fabrication and the current state of the laser gate project. This research was funded in part by the University of Michigan, a Faculty Development Grant from the NRC, and Sandia National Laboratories under DOE-NNSA contract DE-NA0003525.

First demonstration of laser engagement of 1-Hz-injected flying pellets and neutron generation.

PubMed

Komeda, Osamu; Nishimura, Yasuhiko; Mori, Yoshitaka; Hanayama, Ryohei; Ishii, Katsuhiro; Nakayama, Suisei; Kitagawa, Yoneyoshi; Sekine, Takashi; Sato, Nakahiro; Kurita, Takashi; Kawashima, Toshiyuki; Kan, Hirofumi; Nakamura, Naoki; Kondo, Takuya; Fujine, Manabu; Azuma, Hirozumi; Motohiro, Tomoyoshi; Hioki, Tatsumi; Kakeno, Mitsutaka; Sunahara, Atsushi; Sentoku, Yasuhiko; Miura, Eisuke

2013-01-01

Pellet injection and repetitive laser illumination are key technologies for realizing inertial fusion energy. Numerous studies have been conducted on target suppliers, injectors, and tracking systems for flying pellet engagement. Here we for the first time demonstrate the pellet injection, counter laser beams' engagement and neutron generation. Deuterated polystyrene (CD) bead pellets, after free-falling for a distance of 18 cm at 1 Hz, are successfully engaged by two counter laser beams from a diode-pumped, ultra-intense laser HAMA. The laser energy, pulse duration, wavelength, and the intensity are 0.63 J per beam, 104 fs, and 811 nm, 4.7 × 10(18) W/cm(2), respectively. The irradiated pellets produce D(d,n)(3)He-reacted neutrons with a maximum yield of 9.5 × 10(4)/4π sr/shot. Moreover, the laser is found out to bore a straight channel with 10 μm-diameter through the 1-mm-diameter beads. The results indicate potentially useful technologies and findings for the next step in realizing inertial fusion energy.

First demonstration of laser engagement of 1-Hz-injected flying pellets and neutron generation

PubMed Central

Komeda, Osamu; Nishimura, Yasuhiko; Mori, Yoshitaka; Hanayama, Ryohei; Ishii, Katsuhiro; Nakayama, Suisei; Kitagawa, Yoneyoshi; Sekine, Takashi; Sato, Nakahiro; Kurita, Takashi; Kawashima, Toshiyuki; Kan, Hirofumi; Nakamura, Naoki; Kondo, Takuya; Fujine, Manabu; Azuma, Hirozumi; Motohiro, Tomoyoshi; Hioki, Tatsumi; Kakeno, Mitsutaka; Sunahara, Atsushi; Sentoku, Yasuhiko; Miura, Eisuke

2013-01-01

Pellet injection and repetitive laser illumination are key technologies for realizing inertial fusion energy. Numerous studies have been conducted on target suppliers, injectors, and tracking systems for flying pellet engagement. Here we for the first time demonstrate the pellet injection, counter laser beams' engagement and neutron generation. Deuterated polystyrene (CD) bead pellets, after free-falling for a distance of 18 cm at 1 Hz, are successfully engaged by two counter laser beams from a diode-pumped, ultra-intense laser HAMA. The laser energy, pulse duration, wavelength, and the intensity are 0.63 J per beam, 104 fs, and 811 nm, 4.7 × 1018 W/cm2, respectively. The irradiated pellets produce D(d,n)3He-reacted neutrons with a maximum yield of 9.5 × 104/4π sr/shot. Moreover, the laser is found out to bore a straight channel with 10 μm-diameter through the 1-mm-diameter beads. The results indicate potentially useful technologies and findings for the next step in realizing inertial fusion energy. PMID:24008696

Quasi-monoenergetic ion generation by hole-boring radiation pressure acceleration in inhomogeneous plasmas using tailored laser pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weng, S. M., E-mail: weng-sm@ile.osaka-u.ac.jp; Murakami, M.; Azechi, H.

It is proposed that laser hole-boring at a steady speed in inhomogeneous overdense plasma can be realized by the use of temporally tailored intense laser pulses, producing high-fluence quasi-monoenergetic ion beams. A general temporal profile of such laser pulses is formulated for arbitrary plasma density distribution. As an example, for a precompressed deuterium-tritium fusion target with an exponentially increasing density profile, its matched laser profile for steady hole-boring is given theoretically and verified numerically by particle-in-cell simulations. Furthermore, we propose to achieve fast ignition by the in-situ hole-boring accelerated ions using a tailored laser pulse. Simulations show that the effectivemore » energy fluence, conversion efficiency, energy spread, and collimation of the resulting ion beam can be significantly improved as compared to those found with un-tailored laser profiles. For the fusion fuel with an areal density of 1.5 g cm{sup –2}, simulation indicates that it is promising to realize fast ion ignition by using a tailored driver pulse with energy about 65 kJ.« less

Indirect drive targets for fusion power

DOEpatents

Amendt, Peter A.; Miles, Robin R.

2016-10-11

A hohlraum for an inertial confinement fusion power plant is disclosed. The hohlraum includes a generally cylindrical exterior surface, and an interior rugby ball-shaped surface. Windows over laser entrance holes at each end of the hohlraum enclose inert gas. Infrared reflectors on opposite sides of the central point reflect fusion chamber heat away from the capsule. P2 shields disposed on the infrared reflectors help assure an enhanced and more uniform x-ray bath for the fusion fuel capsule.

Effects of electron-ion temperature equilibration on inertial confinement fusion implosions.

PubMed

Xu, Barry; Hu, S X

2011-07-01

The electron-ion temperature relaxation essentially affects both the laser absorption in coronal plasmas and the hot-spot formation in inertial confinement fusion (ICF). It has recently been reexamined for plasma conditions closely relevant to ICF implosions using either classical molecular-dynamics simulations or analytical methods. To explore the electron-ion temperature equilibration effects on ICF implosion performance, we have examined two Coulomb logarithm models by implementing them into our hydrocodes, and we have carried out hydrosimulations for ICF implosions. Compared to the Lee-More model that is currently used in our standard hydrocodes, the two models predict substantial differences in laser absorption, coronal temperatures, and neutron yields for ICF implosions at the OMEGA Laser Facility [Boehly et al. Opt. Commun. 133, 495 (1997)]. Such effects on the triple-picket direct-drive design at the National Ignition Facility (NIF) have also been explored. Based on the validity of the two models, we have proposed a combined model of the electron-ion temperature-relaxation rate for the overall ICF plasma conditions. The hydrosimulations using the combined model for OMEGA implosions have shown ∼6% more laser absorption, ∼6%-15% higher coronal temperatures, and ∼10% more neutron yield, when compared to the Lee-More model prediction. It is also noticed that the gain for the NIF direct-drive design can be varied by ∼10% among the different electron-ion temperature-relaxation models.

Residual stress prediction in a powder bed fusion manufactured Ti6Al4V hip stem

NASA Astrophysics Data System (ADS)

Barrett, Richard A.; Etienne, Titouan; Duddy, Cormac; Harrison, Noel M.

2017-10-01

Powder bed fusion (PBF) is a category of additive manufacturing (AM) that is particularly suitable for the production of 3D metallic components. In PBF, only material in the current build layer is at the required melt temperature, with the previously melted and solidified layers reducing in temperature, thus generating a significant thermal gradient within the metallic component, particularly for laser based PBF components. The internal thermal stresses are subsequently relieved in a post-processing heat-treatment step. Failure to adequately remove these stresses can result in cracking and component failure. A prototype hip stem was manufactured from Ti6Al4V via laser PBF but was found to have fractured during over-seas shipping. This study examines the evolution of thermal stresses during the laser PBF manufacturing and heat treatment processes of the hip stem in a 2D finite element analysis (FEA) and compares it to an electron beam PBF process. A custom written script for the automatic conversion of a gross geometry finite element model into a thin layer- by-layer finite element model was developed. The build process, heat treatment (for laser PBF) and the subsequent cooling were simulated at the component level. The results demonstrate the effectiveness of the heat treatment in reducing PBF induced thermal stresses, and the concentration of stresses in the region that fractured.

Canonical Descriptions of High Intensity Laser-Plasma Interaction

NASA Astrophysics Data System (ADS)

Le Cornu, B. J.

The problem of laser-plasma interaction has been studied extensively in the context of inertial confinement fusion (ICF). These studies have focussed on effects like the nonlinear force, self-focusing, Rayleigh- Taylor instabilities, stimulated Brillouin scattering and stimulated Raman scattering observed in ICF schemes. However, there remains a large discrepancy between theory and experiment in the context of nuclear fusion schemes. Several authors have attempted to gain greater understanding of the physics involved by the application of standard or 'canonical' methods used in Lagrangian and Hamiltonian mechanics to the problem of plasma physics. This thesis presents a new canonical description of laser-plasma interaction based on the Podolsky Lagrangian. Finite self-energy of charged particles, incroporation of high-frequency effects and an ability to quantise are the main advantages of this new model. The nature of the Podolsky constant is also analysed in the context of plasma physics, specifically in terms of the plasma dispersion relation. A new gauge invariant expression of the energy-momentum tensor for any gauge invariant Lagrangian dependent on second order derivatives is derived for the first time. Finally, the transient and nontransient expressions of the nonlinear ponderomotive force in laser-plasma interaction are discussed and shown to be closely approximated by a canonical derivation of the electromagnetic Lagrangian, a fact that seems to have been missed in the literature.

Odometry and Laser Scanner Fusion Based on a Discrete Extended Kalman Filter for Robotic Platooning Guidance

PubMed Central

Espinosa, Felipe; Santos, Carlos; Marrón-Romera, Marta; Pizarro, Daniel; Valdés, Fernando; Dongil, Javier

2011-01-01

This paper describes a relative localization system used to achieve the navigation of a convoy of robotic units in indoor environments. This positioning system is carried out fusing two sensorial sources: (a) an odometric system and (b) a laser scanner together with artificial landmarks located on top of the units. The laser source allows one to compensate the cumulative error inherent to dead-reckoning; whereas the odometry source provides less pose uncertainty in short trajectories. A discrete Extended Kalman Filter, customized for this application, is used in order to accomplish this aim under real time constraints. Different experimental results with a convoy of Pioneer P3-DX units tracking non-linear trajectories are shown. The paper shows that a simple setup based on low cost laser range systems and robot built-in odometry sensors is able to give a high degree of robustness and accuracy to the relative localization problem of convoy units for indoor applications. PMID:22164079

Odometry and laser scanner fusion based on a discrete extended Kalman Filter for robotic platooning guidance.

PubMed

Espinosa, Felipe; Santos, Carlos; Marrón-Romera, Marta; Pizarro, Daniel; Valdés, Fernando; Dongil, Javier

2011-01-01

This paper describes a relative localization system used to achieve the navigation of a convoy of robotic units in indoor environments. This positioning system is carried out fusing two sensorial sources: (a) an odometric system and (b) a laser scanner together with artificial landmarks located on top of the units. The laser source allows one to compensate the cumulative error inherent to dead-reckoning; whereas the odometry source provides less pose uncertainty in short trajectories. A discrete Extended Kalman Filter, customized for this application, is used in order to accomplish this aim under real time constraints. Different experimental results with a convoy of Pioneer P3-DX units tracking non-linear trajectories are shown. The paper shows that a simple setup based on low cost laser range systems and robot built-in odometry sensors is able to give a high degree of robustness and accuracy to the relative localization problem of convoy units for indoor applications.

Method for foam encapsulating laser targets

DOEpatents

Hendricks, Charles D.

1977-01-01

Foam encapsulated laser fusion targets are made by positioning a fusion fuel-filled sphere within a mold cavity of suitable configuration and dimensions, and then filling the cavity with a material capable of producing a low density, microcellular foam, such as cellulose acetate dissolved in an acetone-based solvent. The mold assembly is dipped into an ice water bath to gel the material and thereafter soaked in the water bath to leach out undesired components, after which the gel is frozen, then freeze-dried wherein water and solvents sublime and the gel structure solidifies into a low-density microcellular foam, thereafter the resulting foam encapsulated target is removed from the mold cavity. The fuel-filled sphere is surrounded by foam having a thickness of about 10 to 100 .mu.m, a cell size of less than 2 .mu.m, and density of 0.065 to 0.6 .times. 10.sup.3 kg/m.sup.3. Various configured foam-encapsulated targets capable of being made by this encapsulation method are illustrated.

Optical design and Initial Results from The National Institute of Standards and Technology’s AMMT/TEMPS Facility

PubMed Central

Grantham, Steven; Lane, Brandon; Neira, Jorge; Mekhontsev, Sergey; Vlasea, Mihaela; Hanssen, Leonard

2017-01-01

The National Institute of Standards and Technology’s (NIST) Physical Measurement and Engineering Laboratories are jointly developing the Additive Manufacturing Measurement Testbed (AMMT)/ Temperature and Emittance of Melts, Powders and Solids (TEMPS) facilities. These facilities will be co-located on an open architecture laser-based powder bed fusion system allowing users full access to the system’s operation parameters. This will provide users with access to machine-independent monitoring and control of the powder bed fusion process. In this paper there will be emphasis on the AMMT, which incorporates in-line visible light collection optics for monitoring and feedback control of the powder bed fusion process. We shall present an overview of the AMMT/TEMPS program and its goals. The optical and mechanical design of the open architecture powder-bed fusion system and the AMMT will also be described. In addition, preliminary measurement results from the system along with the current status of the system will be described. PMID:28579666

X-ray conversion efficiency of high-Z hohlraum wall materials for indirect drive ignition

NASA Astrophysics Data System (ADS)

Dewald, E. L.; Rosen, M.; Glenzer, S. H.; Suter, L. J.; Girard, F.; Jadaud, J. P.; Schein, J.; Constantin, C.; Wagon, F.; Huser, G.; Neumayer, P.; Landen, O. L.

2008-07-01

The conversion efficiency of 351nm laser light to soft x rays (0.1-5keV) was measured for Au, U, and high Z mixture "cocktails" used as hohlraum wall materials in indirect drive fusion experiments. For the spherical targets in a direct drive geometry, flattop laser pulses and laser smoothing with phase plates are employed to achieve constant and uniform laser intensities of 1014 and 1015W/cm2 over the target surface that are relevant for the future ignition experiments at the National Ignition Facility [G. H. Miller, E. I. Moses, and C. R. Wuest, Nucl. Fusion 44, 228 (2004)]. The absolute time and spectrally resolved radiation flux is measured with a multichannel soft x-ray power diagnostic. The conversion efficiency is then calculated by dividing the measured x-ray power by the incident laser power from which the measured laser backscattering losses are subtracted. After ˜0.5ns, the time resolved x-ray conversion efficiency reaches a slowly increasing plateau of 95% at 1014W/cm2 laser intensity and of 80% at 1015W/cm2. The M-band flux (2-5keV) is negligible at 1014W/cm2 reaching ˜1% of the total x-ray flux for all target materials. In contrast, the M-band flux is significant and depends on the target material at 1015W/cm2 laser intensity, reaching values between 10% of the total flux for U and 27% for Au. LASNEX simulations [G. B. Zimmerman and W. L. Kruer, Comm. Plasma Phys. Contr. Fusion 2, 51 (1975)] show good agreement in conversion efficiency and radiated spectra with data when using XSN atomic physics model and a flux limiter of 0.15, but they underestimate the generated M-band flux.

Demonstration of Ion Kinetic Effects in Inertial Confinement Fusion Implosions and Investigation of Magnetic Reconnection Using Laser-Produced Plasmas

NASA Astrophysics Data System (ADS)

Rosenberg, M. J.

2016-10-01

Shock-driven laser inertial confinement fusion (ICF) implosions have demonstrated the presence of ion kinetic effects in ICF implosions and also have been used as a proton source to probe the strongly driven reconnection of MG magnetic fields in laser-generated plasmas. Ion kinetic effects arise during the shock-convergence phase of ICF implosions when the mean free path for ion-ion collisions (λii) approaches the size of the hot-fuel region (Rfuel) and may impact hot-spot formation and the possibility of ignition. To isolate and study ion kinetic effects, the ratio of N - K =λii /Rfuel was varied in D3He-filled, shock-driven implosions at the Omega Laser Facility and the National Ignition Facility, from hydrodynamic-like conditions (NK 0.01) to strongly kinetic conditions (NK 10). A strong trend of decreasing fusion yields relative to the predictions of hydrodynamic models is observed as NK increases from 0.1 to 10. Hydrodynamics simulations that include basic models of the kinetic effects that are likely to be present in these experiments-namely, ion diffusion and Knudsen-layer reduction of the fusion reactivity-are better able to capture the experimental results. This type of implosion has also been used as a source of monoenergetic 15-MeV protons to image magnetic fields driven to reconnect in laser-produced plasmas at conditions similar to those encountered at the Earth's magnetopause. These experiments demonstrate that for both symmetric and asymmetric magnetic-reconnection configurations, when plasma flows are much stronger than the nominal Alfvén speed, the rate of magnetic-flux annihilation is determined by the flow velocity and is largely insensitive to initial plasma conditions. This work was supported by the Department of Energy Grant Number DENA0001857.

An Accurate Non-Cooperative Method for Measuring Textureless Spherical Target Based on Calibrated Lasers.

PubMed

Wang, Fei; Dong, Hang; Chen, Yanan; Zheng, Nanning

2016-12-09

Strong demands for accurate non-cooperative target measurement have been arising recently for the tasks of assembling and capturing. Spherical objects are one of the most common targets in these applications. However, the performance of the traditional vision-based reconstruction method was limited for practical use when handling poorly-textured targets. In this paper, we propose a novel multi-sensor fusion system for measuring and reconstructing textureless non-cooperative spherical targets. Our system consists of four simple lasers and a visual camera. This paper presents a complete framework of estimating the geometric parameters of textureless spherical targets: (1) an approach to calibrate the extrinsic parameters between a camera and simple lasers; and (2) a method to reconstruct the 3D position of the laser spots on the target surface and achieve the refined results via an optimized scheme. The experiment results show that our proposed calibration method can obtain a fine calibration result, which is comparable to the state-of-the-art LRF-based methods, and our calibrated system can estimate the geometric parameters with high accuracy in real time.

An Accurate Non-Cooperative Method for Measuring Textureless Spherical Target Based on Calibrated Lasers

PubMed Central

Wang, Fei; Dong, Hang; Chen, Yanan; Zheng, Nanning

2016-01-01

Strong demands for accurate non-cooperative target measurement have been arising recently for the tasks of assembling and capturing. Spherical objects are one of the most common targets in these applications. However, the performance of the traditional vision-based reconstruction method was limited for practical use when handling poorly-textured targets. In this paper, we propose a novel multi-sensor fusion system for measuring and reconstructing textureless non-cooperative spherical targets. Our system consists of four simple lasers and a visual camera. This paper presents a complete framework of estimating the geometric parameters of textureless spherical targets: (1) an approach to calibrate the extrinsic parameters between a camera and simple lasers; and (2) a method to reconstruct the 3D position of the laser spots on the target surface and achieve the refined results via an optimized scheme. The experiment results show that our proposed calibration method can obtain a fine calibration result, which is comparable to the state-of-the-art LRF-based methods, and our calibrated system can estimate the geometric parameters with high accuracy in real time. PMID:27941705

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Li; Gu, Chun; Xu, Lixin, E-mail: xulixin@ustc.edu.cn

The self-adapting algorithms are improved to optimize a beam configuration in the direct drive laser fusion system with the solid state lasers. A configuration of 32 laser beams is proposed for achieving a high uniformity illumination, with a root-mean-square deviation at 10{sup −4} level. In our optimization, the parameters such as beam number, beam arrangement, and beam intensity profile are taken into account. The illumination uniformity robustness versus the parameters such as intensity profile deviations, power imbalance, intensity profile noise, the pointing error, and the target position error is also discussed. In this study, the model is assumed a solid-spheremore » illumination, and refraction effects of incident light on the corona are not considered. Our results may have a potential application in the design of the direct-drive laser fusion of the Shen Guang-II Upgrading facility (SG-II-U, China).« less

DPSSL pumped 20-TW Ti:sapphire laser system for DD fusion experiment

NASA Astrophysics Data System (ADS)

Sekine, T.; Hatano, Y.; Takeuchi, Y.; Kawashima, T.

2016-03-01

A diode-pumped solid-state laser (DPSSL) pumped 20-TW output Ti:sapphire laser system has been developed. A diode-pumped Nd:glass laser with output energy of 12.7 J in 527 nm was used as a pump source for a 20-TW Ti:sapphire amplifier. A CeLiB6O10 nonlinear optical crystal was used as a frequency doubler of the Nd:glass DPSSL[1]. Figure 1 shows typical output pulse energy of the 20-TW amplifier as a function of pumping energy and a near field pattern. A 1.65 J pulse energy was obtained by 4.5 J pump energy. The amplified seed pulse is compressed to typically 60 fs as shown in Fig. 1 by a vacuumed pulse compressor with 80% of transmissivity. Encircled energy ratio, into a circled with 8 μm diameter area, of far field pattern focused by off-axis parabolic mirror with F# of 3 is numerically evaluated to 40% at TW class output condition. Then focal intensity would reach to 1018W/cm2. This all- DPSSL system contributes for stable and continual investigation of laser induced plasma experiment. We have succeeded continual and high efficient generation of DD fusion neutron from CD nano-particles by cluster fusion scheme using the 20-TW laser. A yield of ∼105 neutrons per shot was stably observed during continuous 100 shots with repetition rate of 0.1Hz.

Laser etching of austenitic stainless steels for micro-structural evaluation

NASA Astrophysics Data System (ADS)

Baghra, Chetan; Kumar, Aniruddha; Sathe, D. B.; Bhatt, R. B.; Behere, P. G.; Afzal, Mohd

2015-06-01

Etching is a key step in metallography to reveal microstructure of polished specimen under an optical microscope. A conventional technique for producing micro-structural contrast is chemical etching. As an alternate, laser etching is investigated since it does not involve use of corrosive reagents and it can be carried out without any physical contact with sample. Laser induced etching technique will be beneficial especially in nuclear industry where materials, being radioactive in nature, are handled inside a glove box. In this paper, experimental results of pulsed Nd-YAG laser based etching of few austenitic stainless steels such as SS 304, SS 316 LN and SS alloy D9 which are chosen as structural material for fabrication of various components of upcoming Prototype Fast Breeder Reactor (PFBR) at Kalpakkam India were reported. Laser etching was done by irradiating samples using nanosecond pulsed Nd-YAG laser beam which was transported into glass paneled glove box using optics. Experiments were carried out to understand effect of laser beam parameters such as wavelength, fluence, pulse repetition rate and number of exposures required for etching of austenitic stainless steel samples. Laser etching of PFBR fuel tube and plug welded joint was also carried to evaluate base metal grain size, depth of fusion at welded joint and heat affected zone in the base metal. Experimental results demonstrated that pulsed Nd-YAG laser etching is a fast and effortless technique which can be effectively employed for non-contact remote etching of austenitic stainless steels for micro-structural evaluation.

Vertical-Cavity Surface-Emitting 1.55-μm Lasers Fabricated by Fusion

NASA Astrophysics Data System (ADS)

Babichev, A. V.; Karachinskii, L. Ya.; Novikov, I. I.; Gladyshev, A. G.; Blokhin, S. A.; Mikhailov, S.; Iakovlev, V.; Sirbu, A.; Stepniak, G.; Chorchos, L.; Turkiewicz, J. P.; Voropaev, K. O.; Ionov, A. S.; Agustin, M.; Ledentsov, N. N.; Egorov, A. Yu.

2018-01-01

The results of studies on fabrication of vertical-cavity surface-emitting 1.55-μm lasers by fusing AlGaAs/GaAs distributed-Bragg-reflector wafers and an active region based on thin In0.74Ga0.26 As quantum wells grown by molecular-beam epitaxy are presented. Lasers with a current aperture diameter of 8 μm exhibit continuous lasing with a threshold current below 1.5 mA, an output optical power of 6 mW, and an efficiency of approximately 22%. Single-mode lasing with a side-mode suppression ratio of 40-45 dB is observed in the entire operating current range. The effective modulation frequency of these lasers is as high as 9 GHz and is limited by the low parasitic cutoff frequency and self-heating.

Reduction of Surface Roughness by Means of Laser Processing over Additive Manufacturing Metal Parts.

PubMed

Alfieri, Vittorio; Argenio, Paolo; Caiazzo, Fabrizia; Sergi, Vincenzo

2016-12-31

Optimization of processing parameters and exposure strategies is usually performed in additive manufacturing to set up the process; nevertheless, standards for roughness may not be evenly matched on a single complex part, since surface features depend on the building direction of the part. This paper aims to evaluate post processing treating via laser surface modification by means of scanning optics and beam wobbling to process metal parts resulting from selective laser melting of stainless steel in order to improve surface topography. The results are discussed in terms of roughness, geometry of the fusion zone in the cross-section, microstructural modification, and microhardness so as to assess the effects of laser post processing. The benefits of beam wobbling over linear scanning processing are shown, as heat effects in the base metal are proven to be lower.

Reduction of Surface Roughness by Means of Laser Processing over Additive Manufacturing Metal Parts

PubMed Central

Alfieri, Vittorio; Argenio, Paolo; Caiazzo, Fabrizia; Sergi, Vincenzo

2016-01-01

Optimization of processing parameters and exposure strategies is usually performed in additive manufacturing to set up the process; nevertheless, standards for roughness may not be evenly matched on a single complex part, since surface features depend on the building direction of the part. This paper aims to evaluate post processing treating via laser surface modification by means of scanning optics and beam wobbling to process metal parts resulting from selective laser melting of stainless steel in order to improve surface topography. The results are discussed in terms of roughness, geometry of the fusion zone in the cross-section, microstructural modification, and microhardness so as to assess the effects of laser post processing. The benefits of beam wobbling over linear scanning processing are shown, as heat effects in the base metal are proven to be lower. PMID:28772380

Measuring the Refractive Index of a Laser-Plasma Optical System

NASA Astrophysics Data System (ADS)

Turnbull, D.; Goyon, C.; Pollock, B. B.; Mariscal, D.; Divol, L.; Ross, J. S.; Patankar, S.; Kemp, G. E.; Moody, J. D.; Michel, P. A.

2016-10-01

We report the first complete set of measurements of a laser-plasma optical system's refractive index, as seen by an independent probe laser beam, as a function of the relative wavelength shift between the two laser beams. Both the imaginary and real refractive-index components are found to be in good agreement with linear theory using plasma parameters measured by optical Thomson scattering and interferometry; the former is in contrast to previous work and has implications for cross-beam energy transfer in indirect-drive inertial confinement fusion, and the latter is measured for the first time. The data include the first demonstration of a laser-plasma polarizer with 85% to 87% extinction for the particular laser and plasma parameters used in this experiment, complementing the existing suite of high-power, tunable, and ultrafast plasma-based photonic devices. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Possible application of electromagnetic guns to impact fusion

NASA Astrophysics Data System (ADS)

Kostoff, R. N.; Peaslee, A. T., Jr.; Ribe, F. L.

1982-01-01

The possible application of electromagnetic guns to impact fusion for the generation of electric power is discussed, and advantages of impact fusion over the more conventional inertial confinement fusion concepts are examined. It is shown that impact fusion can achieve the necessary high yields, of the order of a few gigajoules, which are difficult to achieve with lasers except at unrealistically high target gains. The rail gun accelerator is well adapted to the delivery of some 10-100 megajoules of energy to the fusion target, and the electrical technology involved is relatively simple: inductive storage or rotating machinery and capacitors. It is concluded that the rail gun has the potential of developing into an impact fusion macroparticle accelerator.

On the Mechanisms for Martensite Formation in YAG Laser Welded Austenitic NiTi

NASA Astrophysics Data System (ADS)

Oliveira, J. P.; Braz Fernandes, F. M.; Miranda, R. M.; Schell, N.

2016-03-01

Extensive work has been reported on the microstructure of laser-welded NiTi alloys either superelastic or with shape memory effect, motivated by the fact that the microstructure affects the functional properties. However, some effects of laser beam/material interaction with these alloys have not yet been discussed. This paper aims to discuss the mechanisms for the occurrence of martensite in the heat-affected zone and in the fusion zone at room temperature, while the base material is fully austenitic. For this purpose, synchrotron radiation was used together with a simple thermal analytic mathematical model. Two distinct mechanisms are proposed for the presence of martensite in different zones of a weld, which affects the mechanical and functional behavior of a welded component.

Optimised design for a 1 kJ diode-pumped solid-state laser system

NASA Astrophysics Data System (ADS)

Mason, Paul D.; Ertel, Klaus; Banerjee, Saumyabrata; Phillips, P. Jonathan; Hernandez-Gomez, Cristina; Collier, John L.

2011-06-01

A conceptual design for a kJ-class diode-pumped solid-state laser (DPSSL) system based on cryogenic gas-cooled multislab ceramic Yb:YAG amplifier technology has been developed at the STFC as a building block towards a MJ-class source for inertial fusion energy (IFE) projects such as HiPER. In this paper, we present an overview of an amplifier design optimised for efficient generation of 1 kJ nanosecond pulses at 10 Hz repetition rate. In order to confirm the viability of this technology, a prototype version of this amplifier scaled to deliver 10 J at 10 Hz, DiPOLE, is under development at the Central Laser Facility. A progress update on the status of this system is also presented.

Comparison of aged polyamide powders for selective laser sintering

NASA Astrophysics Data System (ADS)

Martínez, A.; Ibáñez, A.; Sánchez, A.; León, M. A.

2012-04-01

Selective Laser Sintering (SLS) is an additive manufacturing technology in which a three-dimensional object is manufactured layer by layer by melting powder materials with heat generated from a CO2 laser. However, a disadvantage of sintered materials is that the unsintered powder material during the process can be reused only a limited number of cycles, as during the heating phase in the sintering chamber the material remains at a temperature near the fusion point for a certain period of time and lose properties. This work shows the study of two polyamides (PA12)-based powders used in SLS with the aim of understanding the modification of their properties mainly with the temperature and the time at which they are exposed during the processing.

Hard X-ray Imaging for Measuring Laser Absorption Spatial Profiles on the National Ignition Facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dewald, E L; Jones, O S; Landen, O L

2006-04-25

Hard x-ray (''Thin wall'') imaging will be employed on the National Ignition Facility (NIF) to spatially locate laser beam energy deposition regions on the hohlraum walls in indirect drive Inertial Confinement Fusion (ICF) experiments, relevant for ICF symmetry tuning. Based on time resolved imaging of the hard x-ray emission of the laser spots, this method will be used to infer hohlraum wall motion due to x-ray and laser ablation and any beam refraction caused by plasma density gradients. In optimizing this measurement, issues that have to be addressed are hard x-ray visibility during the entire ignition laser pulse with intensitiesmore » ranging from 10{sup 13} to 10{sup 15} W/cm{sup 2}, as well as simultaneous visibility of the inner and the outer laser drive cones. In this work we will compare the hard x-ray emission calculated by LASNEX and analytical modeling with thin wall imaging data recorded previously on Omega and during the first hohlraum experiments on NIF. Based on these calculations and comparisons the thin wall imaging will be optimized for ICF/NIF experiments.« less

Method for the controlled liberation of fusion nuclear energy (in French)

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

1972-08-18

L'invention concerne des reactions thermonucleaires. Elle se rapporte a un procede de fusion dans lequel de l'energie laser est concentree sur de minuscules spheres de combustible forme de deuterium et de tritium, de maniere a creer d'une part un plasma superficiel assurant un transfert efficace d'energie et d'autre part des ondes de choc convergeant au centre et assurant la fusion nucleaire de la matiere centrale. Ceci est applicable a la production d'energie thermique par fusion nucleaire. (FR)

Status and future prospects of laser fusion and high power laser applications

NASA Astrophysics Data System (ADS)

Mima, Kunioki

2010-08-01

In Asia, there are many institutes for the R&D of high power laser science and applications. They are 5 major institutes in Japan, 4 major institutes in China, 2 institutes in Korea, and 3 institutes in India. The recent achievements and future prospects of those institutes will be over viewed. In the laser fusion research, the FIREX-I project in Japan has been progressing. The 10kJ short pulse LFEX laser has completed and started the experiments with a single beam. About 1kJ pulse energy will be injected into a cone target. The experimental results of the FIREX experiments will be presented. As the target design for the experiments, a new target, namely, a double cone target was proposed, in which the high energy electrons are well confined and the heating efficiency is significantly improved. Together with the fusion experiments, Osaka University has carried out laboratory astrophysics experiments on photo ionizing plasmas to observe a unique X-ray spectrum from non-LTE plasmas. In 2008, Osaka university has started a new Photon research center in relation with the new program: Consortium for Photon Science and Technology: C-PhoST, in which ultra intense laser plasmas research and related education will be carried out for 10 years. At APRI, JAEA, the fundamental science on the relativistic laser plasmas and the applications of laser particle acceleration has been developed. The application of laser ion acceleration has been investigated on the beam cancer therapy since 2007. In China, The high power glass laser: Shenguan-II and a peta watt beam have been operated to work on radiation hydro dynamics at SIOFM Shanghai. The laser material and optics are developed at SIOFM and LFRC. The IAPCM and the IOP continued the studies on radiation hydrodynamics and on relativistic laser plasmas interactions. At LFRC in China, the construction of Shenguan III glass laser of 200kJ in blue has progressed and will be completed in 2012. Together with the Korean program, I will overview the above Asian programs.

Soft X-ray imaging of thick carbon-based materials using the normal incidence multilayer optics.

PubMed

Artyukov, I A; Feschenko, R M; Vinogradov, A V; Bugayev, Ye A; Devizenko, O Y; Kondratenko, V V; Kasyanov, Yu S; Hatano, T; Yamamoto, M; Saveliev, S V

2010-10-01

The high transparency of carbon-containing materials in the spectral region of "carbon window" (lambda approximately 4.5-5nm) introduces new opportunities for various soft X-ray microscopy applications. The development of efficient multilayer coated X-ray optics operating at the wavelengths of about 4.5nm has stimulated a series of our imaging experiments to study thick biological and synthetic objects. Our experimental set-up consisted of a laser plasma X-ray source generated with the 2nd harmonics of Nd-glass laser, scandium-based thin-film filters, Co/C multilayer mirror and X-ray film UF-4. All soft X-ray images were produced with a single nanosecond exposure and demonstrated appropriate absorption contrast and detector-limited spatial resolution. A special attention was paid to the 3D imaging of thick low-density foam materials to be used in design of laser fusion targets.

Raman accumulator as a fusion laser driver

DOEpatents

George, E. Victor; Swingle, James C.

1985-01-01

Apparatus for simultaneous laser pulse amplification and compression, using multiple pass Raman scattering in one Raman cell and pulse switchout from the optical cavity through use of a dichroic device associated with the Raman cell.

Raman accumulator as a fusion laser driver

DOEpatents

George, E.V.; Swingle, J.C.

1982-03-31

Apparatus for simultaneous laser pulse amplification and compression, using multiple pass Raman scattering in one Raman cell and pulse switchout from the optical cavity through use of a dichroic device associated with the Raman cell.

Microstructure and Mechanical Properties of Hybrid Welded Joints with Laser and CO2-Shielded Arc

NASA Astrophysics Data System (ADS)

Wahba, M.; Mizutani, M.; Katayama, S.

2016-07-01

With the objective of reducing the operating costs, argon-rich shielding gas was replaced by 100% CO2 gas in hybrid laser-arc welding of shipbuilding steel. The welding parameters were optimized to obtain buried-arc transfer in order to mitigate spatter formation. Sound butt joints could be successfully produced for plates of 14 and 17 mm thickness in one welding pass. Subsequently, the welded joints were subjected to different tests to evaluate the influence of CO2 shielding gas on the mechanical properties of the welded joints. All tensile-tested specimens failed in the base material, indicating the higher strength of the welded joints. The impact toughness of the welded joints, measured at -20 °C, reached approximately 76% of that of the base material, which was well above the limit set by the relevant standard. The microstructure of the fusion zone consisted of grain boundary ferrite and acicular ferrite uniformly over the plate thickness except for the joint root where the microstructure was chiefly ferrite with an aligned second phase. This resulted in higher hardness in the root region compared with the top and middle parts of the fusion zone.

Synchrotron-Based X-ray Microtomography Characterization of the Effect of Processing Variables on Porosity Formation in Laser Power-Bed Additive Manufacturing of Ti-6Al-4V

NASA Astrophysics Data System (ADS)

Cunningham, Ross; Narra, Sneha P.; Montgomery, Colt; Beuth, Jack; Rollett, A. D.

2017-03-01

The porosity observed in additively manufactured (AM) parts is a potential concern for components intended to undergo high-cycle fatigue without post-processing to remove such defects. The morphology of pores can help identify their cause: irregularly shaped lack of fusion or key-holing pores can usually be linked to incorrect processing parameters, while spherical pores suggest trapped gas. Synchrotron-based x-ray microtomography was performed on laser powder-bed AM Ti-6Al-4V samples over a range of processing conditions to investigate the effects of processing parameters on porosity. The process mapping technique was used to control melt pool size. Tomography was also performed on the powder to measure porosity within the powder that may transfer to the parts. As observed previously in experiments with electron beam powder-bed fabrication, significant variations in porosity were found as a function of the processing parameters. A clear connection between processing parameters and resulting porosity formation mechanism was observed in that inadequate melt pool overlap resulted in lack-of-fusion pores whereas excess power density produced keyhole pores.

Tungsten inert gas (TIG) welding of Ni-rich NiTi plates: functional behavior

NASA Astrophysics Data System (ADS)

Oliveira, J. P.; Barbosa, D.; Braz Fernandes, F. M.; Miranda, R. M.

2016-03-01

It is often reported that, to successfully join NiTi shape memory alloys, fusion-based processes with reduced thermal affected regions (as in laser welding) are required. This paper describes an experimental study performed on the tungsten inert gas (TIG) welding of 1.5 mm thick plates of Ni-rich NiTi. The functional behavior of the joints was assessed. The superelasticity was analyzed by cycling tests at maximum imposed strains of 4, 8 and 12% and for a total of 600 cycles, without rupture. The superelastic plateau was observed, in the stress-strain curves, 30 MPa below that of the base material. Shape-memory effect was evidenced by bending tests with full recovery of the initial shape of the welded joints. In parallel, uniaxial tensile tests of the joints showed a tensile strength of 700 MPa and an elongation to rupture of 20%. The elongation is the highest reported for fusion-welding of NiTi, including laser welding. These results can be of great interest for the wide-spread inclusion of NiTi in complex shaped components requiring welding, since TIG is not an expensive process and is simple to operate and implement in industrial environments.

Microstructure and mechanical properties of friction stir welded and laser welded high entropy alloy CrMnFeCoNi

NASA Astrophysics Data System (ADS)

Jo, Min-Gu; Kim, Han-Jin; Kang, Minjung; Madakashira, Phaniraj P.; Park, Eun Soo; Suh, Jin-Yoo; Kim, Dong-Ik; Hong, Sung-Tae; Han, Heung Nam

2018-01-01

The high entropy alloy CrMnFeCoNi has been shown to have promising structural properties. For a new alloy to be used in a structural application it should be weldable. In the present study, friction stir welding (FSW) and laser welding (LW) techniques were used to butt weld thin plates of CrMnFeCoNi. The microstructure, chemical homogeneity and mechanical behavior of the welds were characterized and compared with the base metal. The tensile stress-strain behavior of the welded specimens were reasonable when compared with that of the base metal. FSW refined the grain size in the weld region by a factor of ˜14 when compared with the base metal. High-angle annular dark field transmission electron microscopy in combination with energy dispersive X-ray spectroscopy showed chemical inhomogeneity between dendritic and interdendritic regions in the fusion zone of LW. Large fluctuations in composition (up to 15 at%) did not change the crystal structure in the fusion zone. Hardness measurements were carried out in the weld cross section and discussed in view of the grain size, low angle grain boundaries and twin boundaries in FSW specimens and the dendritic microstructure in LW specimens.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miley, G.H.

Remarks made in the author{close_quote}s acceptance lecture for the 1995 Edward Teller Medal are presented and expanded. Topics covered include research on nuclear-pumped lasers, the first direct e-beam-pumped laser, direct energy conversion and advanced fuel fusion, plus recent work on inertial electrostatic confinement. {open_quote}{open_quote}Patience{close_quote}{close_quote} and {open_quote}{open_quote}optimism{close_quote}{close_quote} are viewed as essential elements needed by scientists following the {open_quote}{open_quote}zig-zag{close_quote}{close_quote} path to fusion energy production. {copyright} {ital 1996 American Institute of Physics.}

Polar-direct-drive experiments with contoured-shell targets on OMEGA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marshall, F. J.; Radha, P. B.; Bonino, M. J.

Polar-driven direct-drive experiments recently performed on the OMEGA Laser System have demonstrated the efficacy of using a target with a contoured shell with varying thickness to improve the symmetry and fusion performance of the implosion. The polar-driven contoured-shell implosions have substantially reduced low mode perturbations compared to polar-driven spherical-shell implosions as diagnosed by x-ray radiographs up to shell stagnation. As a result, fusion yields were increased by more than a factor of ~2 without increasing the energy of the laser by the use of contoured shells.

Polar-direct-drive experiments with contoured-shell targets on OMEGA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marshall, F. J.; Radha, P. B.; Bonino, M. J.

Polar-driven direct-drive experiments recently performed on the OMEGA Laser System have demonstrated the efficacy of using a target with a contoured shell with varying thickness to improve the symmetry and fusion performance of the implosion. The polar-driven contoured-shell implosions have substantially reduced low mode perturbations compared to polar-driven spherical-shell implosions as diagnosed by x-ray radiographs up to shell stagnation. Fusion yields were increased by more than a factor of ∼2 without increasing the energy of the laser by the use of contoured shells.

Polar-direct-drive experiments with contoured-shell targets on OMEGA

DOE PAGES

Marshall, F. J.; Radha, P. B.; Bonino, M. J.; ...

2016-01-28

Polar-driven direct-drive experiments recently performed on the OMEGA Laser System have demonstrated the efficacy of using a target with a contoured shell with varying thickness to improve the symmetry and fusion performance of the implosion. The polar-driven contoured-shell implosions have substantially reduced low mode perturbations compared to polar-driven spherical-shell implosions as diagnosed by x-ray radiographs up to shell stagnation. As a result, fusion yields were increased by more than a factor of ~2 without increasing the energy of the laser by the use of contoured shells.

Suppressing Two-Plasmon Decay with Laser Frequency Detuning

DOE PAGES

Follett, R. K.; Shaw, J. G.; Myatt, J. F.; ...

2018-03-30

Three-dimensional laser-plasma interaction simulations show that laser frequency detuning by an amount achievable with current laser technology can be used to suppress the two-plasmon decay (TPD) instability and the corresponding hot-electron generation. For the plasma conditions and laser configuration in a direct-drive inertial confinement fusion implosion on the OMEGA laser, the simulations show that ~0.7% laser frequency detuning is sufficient to eliminate TPD-driven hot-electron generation in current experiments. In conclusion, this allows for higher ablation pressures in future implosion designs by using higher laser intensities.

Suppressing Two-Plasmon Decay with Laser Frequency Detuning

DOE Office of Scientific and Technical Information (OSTI.GOV)

Follett, R. K.; Shaw, J. G.; Myatt, J. F.

Three-dimensional laser-plasma interaction simulations show that laser frequency detuning by an amount achievable with current laser technology can be used to suppress the two-plasmon decay (TPD) instability and the corresponding hot-electron generation. For the plasma conditions and laser configuration in a direct-drive inertial confinement fusion implosion on the OMEGA laser, the simulations show that ~0.7% laser frequency detuning is sufficient to eliminate TPD-driven hot-electron generation in current experiments. In conclusion, this allows for higher ablation pressures in future implosion designs by using higher laser intensities.

Suppressing Two-Plasmon Decay with Laser Frequency Detuning

NASA Astrophysics Data System (ADS)

Follett, R. K.; Shaw, J. G.; Myatt, J. F.; Palastro, J. P.; Short, R. W.; Froula, D. H.

2018-03-01

Three-dimensional laser-plasma interaction simulations show that laser frequency detuning by an amount achievable with current laser technology can be used to suppress the two-plasmon decay (TPD) instability and the corresponding hot-electron generation. For the plasma conditions and laser configuration in a direct-drive inertial confinement fusion implosion on the OMEGA laser, the simulations show that ˜0.7 % laser frequency detuning is sufficient to eliminate TPD-driven hot-electron generation in current experiments. This allows for higher ablation pressures in future implosion designs by using higher laser intensities.

Damage resistant optics for a mega-joule solid-state laser

NASA Astrophysics Data System (ADS)

Campbell, J. H.; Rainer, F.; Kozlowski, M. R.; Wolfe, C. R.; Thomas, I.; Milanovich, F.

1990-12-01

Research on Inertial Confinement Fusion (ICF) has progressed rapidly in the past several years. As a consequence, LLNL is developing plans to upgrade the current 120 kJ solid state (Nd3+ phosphate glass) Nova laser to a 1.5 to 2 megajoule system with the goal of achieving fusion ignition. The design of the planned Nova Upgrade is briefly discussed. Because of recent improvements in the damage resistance of optical materials it is now technically and economically feasible to build a megajoule-class solid state laser. Specifically, the damage threshold of Nd(+3)-doped phosphate laser glass, multilayer dielectric coatings, and non-linear optical crystals (e.g., KDP) have been dramatically improved. These materials now meet the fluence requirements for a 1.5 to 2 MJ Nd(+3)-glass laser operating at 1054 and 351 nm and at a pulse length of 3 ns. The recent improvements in damage thresholds are reviewed; threshold data at both 1064 and 355 nm and the measured pulse length scaling are presented.

Damage resistant optics for a megajoule solid state laser

NASA Astrophysics Data System (ADS)

Campbell, Jack H.; Rainer, Frank; Kozlowski, Mark R.; Wolfe, C. Robert; Thomas, Ian M.; Milanovich, Fred P.

1991-06-01

Research on Inertial Confinement Fusion (ICF) has progressed rapidly in the past several years. As a consequence LLNL is developing plans to upgrade the current 120 kJ solid state (Nd3-phosphate glass) Nova laser to a 1 . 5 to 2 megajoule system with the goal of achieving fusion ignition. The design of the planned Nova Upgrade is briefly discussed. Because of recent improvements in the damage resistance of optical materials it is now technically and economically feasible to build a megajoule-class solid state laser. Specifically the damage threshold of Nd3- doped phosphate laser glass muliilayer dielectric coatings and non-linear optical crystals (e. g. KDP) have been dramatically improved. These materials now meet the fluence requirements for a 1. 5-2 MJ Nd3-glass laser operating at 1054 and 351 nm and at a pulse length of 3 ns. The recent improvements in damage thresholds are reviewed threshold data at both 1064 and 355 nm and the measured pulse length scaling are presented. 1.

Metal vapor micro-jet controls material redistribution in laser powder bed fusion additive manufacturing.

PubMed

Ly, Sonny; Rubenchik, Alexander M; Khairallah, Saad A; Guss, Gabe; Matthews, Manyalibo J

2017-06-22

The results of detailed experiments and finite element modeling of metal micro-droplet motion associated with metal additive manufacturing (AM) processes are presented. Ultra high speed imaging of melt pool dynamics reveals that the dominant mechanism leading to micro-droplet ejection in a laser powder bed fusion AM is not from laser induced recoil pressure as is widely believed and found in laser welding processes, but rather from vapor driven entrainment of micro-particles by an ambient gas flow. The physics of droplet ejection under strong evaporative flow is described using simulations of the laser powder bed interactions to elucidate the experimental results. Hydrodynamic drag analysis is used to augment the single phase flow model and explain the entrainment phenomenon for 316 L stainless steel and Ti-6Al-4V powder layers. The relevance of vapor driven entrainment of metal micro-particles to similar fluid dynamic studies in other fields of science will be discussed.

Sensor fusion of cameras and a laser for city-scale 3D reconstruction.

PubMed

Bok, Yunsu; Choi, Dong-Geol; Kweon, In So

2014-11-04

This paper presents a sensor fusion system of cameras and a 2D laser sensorfor large-scale 3D reconstruction. The proposed system is designed to capture data on afast-moving ground vehicle. The system consists of six cameras and one 2D laser sensor,and they are synchronized by a hardware trigger. Reconstruction of 3D structures is doneby estimating frame-by-frame motion and accumulating vertical laser scans, as in previousworks. However, our approach does not assume near 2D motion, but estimates free motion(including absolute scale) in 3D space using both laser data and image features. In orderto avoid the degeneration associated with typical three-point algorithms, we present a newalgorithm that selects 3D points from two frames captured by multiple cameras. The problemof error accumulation is solved by loop closing, not by GPS. The experimental resultsshow that the estimated path is successfully overlaid on the satellite images, such that thereconstruction result is very accurate.

Metal vapor micro-jet controls material redistribution in laser powder bed fusion additive manufacturing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ly, Sonny; Rubenchik, Alexander M.; Khairallah, Saad A.

The results of detailed experiments and finite element modeling of metal micro-droplet motion associated with metal additive manufacturing (AM) processes are presented. Ultra high speed imaging of melt pool dynamics reveals that the dominant mechanism leading to micro-droplet ejection in a laser powder bed fusion AM is not from laser induced recoil pressure as is widely believed and found in laser welding processes, but rather from vapor driven entrainment of micro-particles by an ambient gas flow. The physics of droplet ejection under strong evaporative flow is described using simulations of the laser powder bed interactions to elucidate the experimental results.more » Hydrodynamic drag analysis is used to augment the single phase flow model and explain the entrainment phenomenon for 316 L stainless steel and Ti-6Al-4V powder layers. The relevance of vapor driven entrainment of metal micro-particles to similar fluid dynamic studies in other fields of science will be discussed.« less

Laser-Plasma Interactions on NIKE and the Fusion Test Facility

NASA Astrophysics Data System (ADS)

Phillips, Lee; Weaver, James

2008-11-01

Recent proposed designs for a Fusion Test Facility (FTF) (Obenchain et al., Phys. Plasmas 13 056320 (2006)) for direct-drive ICF targets for energy applications involve high implosion velocities combined with higher laser irradiances. The use of high irradiances increases the likelihood of deleterious laser plasma instabilities (LPI) but the proposed use of a 248 nm KrF laser to drive these targets is expected to minimize the LPI risk. We examine, using simulation results from NRL's FAST hydrocode, the proposed operational regimes of the FTF in relation to the thresholds for the SRS, SBS, and 2-plasmon instabilities. Simulations are also used to help design and interpret ongoing experiments being conducted at NRL's NIKE facility for the purpose of generating and studying LPI. Target geometries and laser pulseshapes were devised in order to create plasma conditions with long scalelengths and low electron temperatures that allow the growth of parametric instabilities. These simulations include the effects of finite beam angles through the use of raytracing.

Metal vapor micro-jet controls material redistribution in laser powder bed fusion additive manufacturing

DOE PAGES

Ly, Sonny; Rubenchik, Alexander M.; Khairallah, Saad A.; ...

2017-06-22

The results of detailed experiments and finite element modeling of metal micro-droplet motion associated with metal additive manufacturing (AM) processes are presented. Ultra high speed imaging of melt pool dynamics reveals that the dominant mechanism leading to micro-droplet ejection in a laser powder bed fusion AM is not from laser induced recoil pressure as is widely believed and found in laser welding processes, but rather from vapor driven entrainment of micro-particles by an ambient gas flow. The physics of droplet ejection under strong evaporative flow is described using simulations of the laser powder bed interactions to elucidate the experimental results.more » Hydrodynamic drag analysis is used to augment the single phase flow model and explain the entrainment phenomenon for 316 L stainless steel and Ti-6Al-4V powder layers. The relevance of vapor driven entrainment of metal micro-particles to similar fluid dynamic studies in other fields of science will be discussed.« less

Fission-Fusion: A new reaction mechanism for nuclear astrophysics based on laser-ion acceleration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thirolf, P. G.; Gross, M.; Allinger, K.

We propose to produce neutron-rich nuclei in the range of the astrophysical r-process around the waiting point N = 126 by fissioning a dense laser-accelerated thorium ion bunch in a thorium target (covered by a CH{sub 2} layer), where the light fission fragments of the beam fuse with the light fission fragments of the target. Via the 'hole-boring' mode of laser Radiation Pressure Acceleration using a high-intensity, short pulse laser, very efficiently bunches of {sup 232}Th with solid-state density can be generated from a Th target and a deuterated CD{sub 2} foil, both forming the production target assembly. Laser-accelerated Thmore » ions with about 7 MeV/u will pass through a thin CH{sub 2} layer placed in front of a thicker second Th foil (both forming the reaction target) closely behind the production target and disintegrate into light and heavy fission fragments. In addition, light ions (d,C) from the CD{sub 2} layer of the production target will be accelerated as well, inducing the fission process of {sup 232}Th also in the second Th layer. The laser-accelerated ion bunches with solid-state density, which are about 10{sup 14} times more dense than classically accelerated ion bunches, allow for a high probability that generated fission products can fuse again. The high ion beam density may lead to a strong collective modification of the stopping power, leading to significant range and thus yield enhancement. Using a high-intensity laser as envisaged for the ELI-Nuclear Physics project in Bucharest (ELI-NP), order-of-magnitude estimates promise a fusion yield of about 10{sup 3} ions per laser pulse in the mass range of A = 180-190, thus enabling to approach the r-process waiting point at N = 126.« less

Model-independent determination of the astrophysical S factor in laser-induced fusion plasmas

NASA Astrophysics Data System (ADS)

Lattuada, D.; Barbarino, M.; Bonasera, A.; Bang, W.; Quevedo, H. J.; Warren, M.; Consoli, F.; De Angelis, R.; Andreoli, P.; Kimura, S.; Dyer, G.; Bernstein, A. C.; Hagel, K.; Barbui, M.; Schmidt, K.; Gaul, E.; Donovan, M. E.; Natowitz, J. B.; Ditmire, T.

2016-04-01

In this work, we present a new and general method for measuring the astrophysical S factor of nuclear reactions in laser-induced plasmas and we apply it to :mmultiscripts>(d ,n )3He . The experiment was performed with the Texas Petawatt Laser, which delivered 150-270 fs pulses of energy ranging from 90 to 180 J to D2 or CD4 molecular clusters (where D denotes 2H ) . After removing the background noise, we used the measured time-of-flight data of energetic deuterium ions to obtain their energy distribution. We derive the S factor using the measured energy distribution of the ions, the measured volume of the fusion plasma, and the measured fusion yields. This method is model independent in the sense that no assumption on the state of the system is required, but it requires an accurate measurement of the ion energy distribution, especially at high energies, and of the relevant fusion yields. In the :mmultiscripts>(d ,n )3He and 3He(d ,p )4He cases discussed here, it is very important to apply the background subtraction for the energetic ions and to measure the fusion yields with high precision. While the available data on both ion distribution and fusion yields allow us to determine with good precision the S factor in the d +d case (lower Gamow energies), for the d +3He case the data are not precise enough to obtain the S factor using this method. Our results agree with other experiments within the experimental error, even though smaller values of the S factor were obtained. This might be due to the plasma environment differing from the beam target conditions in a conventional accelerator experiment.

Model-independent determination of the astrophysical S factor in laser-induced fusion plasmas

DOE PAGES

Lattuada, D.; Barbarino, M.; Bonasera, A.; ...

2016-04-19

In this paper, we present a new and general method for measuring the astrophysical S factor of nuclear reactions in laser-induced plasmas and we apply it to 2H(d,n) 3He. The experiment was performed with the Texas Petawatt Laser, which delivered 150–270 fs pulses of energy ranging from 90 to 180 J to D 2 or CD 4 molecular clusters (where D denotes 2H). After removing the background noise, we used the measured time-of-flight data of energetic deuterium ions to obtain their energy distribution. We derive the S factor using the measured energy distribution of the ions, the measured volume ofmore » the fusion plasma, and the measured fusion yields. This method is model independent in the sense that no assumption on the state of the system is required, but it requires an accurate measurement of the ion energy distribution, especially at high energies, and of the relevant fusion yields. In the 2H(d,n) 3He and 3He(d,p) 4He cases discussed here, it is very important to apply the background subtraction for the energetic ions and to measure the fusion yields with high precision. While the available data on both ion distribution and fusion yields allow us to determine with good precision the S factor in the d+d case (lower Gamow energies), for the d+ 3He case the data are not precise enough to obtain the S factor using this method. Our results agree with other experiments within the experimental error, even though smaller values of the S factor were obtained. This might be due to the plasma environment differing from the beam target conditions in a conventional accelerator experiment.« less

Panoramic 3D Reconstruction by Fusing Color Intensity and Laser Range Data

NASA Astrophysics Data System (ADS)

Jiang, Wei; Lu, Jian

Technology for capturing panoramic (360 degrees) three-dimensional information in a real environment have many applications in fields: virtual and complex reality, security, robot navigation, and so forth. In this study, we examine an acquisition device constructed of a regular CCD camera and a 2D laser range scanner, along with a technique for panoramic 3D reconstruction using a data fusion algorithm based on an energy minimization framework. The acquisition device can capture two types of data of a panoramic scene without occlusion between two sensors: a dense spatio-temporal volume from a camera and distance information from a laser scanner. We resample the dense spatio-temporal volume for generating a dense multi-perspective panorama that has equal spatial resolution to that of the original images acquired using a regular camera, and also estimate a dense panoramic depth-map corresponding to the generated reference panorama by extracting trajectories from the dense spatio-temporal volume with a selecting camera. Moreover, for determining distance information robustly, we propose a data fusion algorithm that is embedded into an energy minimization framework that incorporates active depth measurements using a 2D laser range scanner and passive geometry reconstruction from an image sequence obtained using the CCD camera. Thereby, measurement precision and robustness can be improved beyond those available by conventional methods using either passive geometry reconstruction (stereo vision) or a laser range scanner. Experimental results using both synthetic and actual images show that our approach can produce high-quality panoramas and perform accurate 3D reconstruction in a panoramic environment.

Laser surface fusion of plasma sprayed ceramic turbine seals

NASA Technical Reports Server (NTRS)

Wisander, D. W.; Bill, R. C. (Inventor)

1981-01-01

The thermal shock resistance of a ceramic layer is improved. An improved abradable lining that is deposited on a shroud forming a gas path seal in turbomachinery is emphasized. Improved thermal shock resistance of a shroud is effective through the deliberate introduction of 'benign' cracks. These are microcracks which will not propagate appreciably upon exposure to the thermal shock environment in which a turbine seal must function. Laser surface fusion treatment is used to introduce these microcracks. The ceramic surface is laser scanned to form a continuous dense layer. As this cools and solidifies, shrinkage results in the formation of a very fine crack network. The presence of this deliberately introduced fine crack network precludes the formation of a catastrophic crack during thermal shock exposure.

Fusion pumped laser

DOEpatents

Pappas, Daniel S.

1989-01-01

Apparatus is provided for generating energy in the form of laser radiation. A tokamak fusion reactor is provided for generating a long, or continuous, pulse of high-energy neutrons. The tokamak design provides a temperature and a magnetic field which is effective to generate a neutron flux of at least 10.sup.15 neutrons/cm.sup.2.s. A conversion medium receives neutrons from the tokamak and converts the high-energy neutrons to an energy source with an intensity and an energy effective to excite a preselected lasing medium. The energy source typically comprises fission fragments, alpha particles, and radiation from a fission event. A lasing medium is provided which is responsive to the energy source to generate a population inversion which is effective to support laser oscillations for generating output radiation.

Performance and Mix Measurements of Indirect Drive Cu-Doped Be Implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Casey, D.  T.; Woods, D. T.; Smalyuk, V. A.

2015-05-19

The ablator couples energy between the driver and fusion fuel in inertial confinement fusion (ICF). Because of its low opacity, high solid density, and material properties, beryllium has long been considered an ideal ablator for ICF ignition experiments at the National Ignition Facility. We report here the first indirect drive Be implosions driven with shaped laser pulses and diagnosed with fusion yield at the OMEGA laser. The results show good performance with an average DD neutron yield of ~2 × 10⁹ at a convergence ratio of R₀/R ~ 10 and little impact due to the growth of hydrodynamic instabilities andmore » mix. In addition, the effect of adding an inner liner of W between the Be and DD is demonstrated.« less

Shielding gas effect on weld characteristics in arc-augmented laser welding process of super austenitic stainless steel

NASA Astrophysics Data System (ADS)

Sathiya, P.; Kumar Mishra, Mahendra; Soundararajan, R.; Shanmugarajan, B.

2013-02-01

A series of hybrid welding (gas metal arc welding-CO2 laser beam welding) experiments were conducted on AISI 904L super austenitic stainless steel sheet of 5 mm thickness. A detailed study of CO2 Laser-GMAW hybrid welding experiments with different shielding gas mixtures (100% He, 50% He+50% Ar, 50%He+45% Ar+5% O2, and 45% He+45% Ar+10% N2) were carried out and the results are presented. The resultant welds were subjected to detailed mechanical and microstructural characterization. Hardness testing revealed that the hardness values in the fusion zone were higher than the base material irrespective of the parameters. Transverse tensile testing showed that the joint efficiency is 100% with all the shielding gas experimented. Impact energy values of the welds were also found to be higher than the base material and the fractrograph taken in scanning electron microscope (SEM) has shown that the welds exhibited dimple fracture similar to the base material.

Heating efficiency evaluation with mimicking plasma conditions of integrated fast-ignition experiment.

PubMed

Fujioka, Shinsuke; Johzaki, Tomoyuki; Arikawa, Yasunobu; Zhang, Zhe; Morace, Alessio; Ikenouchi, Takahito; Ozaki, Tetsuo; Nagai, Takahiro; Abe, Yuki; Kojima, Sadaoki; Sakata, Shohei; Inoue, Hiroaki; Utsugi, Masaru; Hattori, Shoji; Hosoda, Tatsuya; Lee, Seung Ho; Shigemori, Keisuke; Hironaka, Youichiro; Sunahara, Atsushi; Sakagami, Hitoshi; Mima, Kunioki; Fujimoto, Yasushi; Yamanoi, Kohei; Norimatsu, Takayoshi; Tokita, Shigeki; Nakata, Yoshiki; Kawanaka, Junji; Jitsuno, Takahisa; Miyanaga, Noriaki; Nakai, Mitsuo; Nishimura, Hiroaki; Shiraga, Hiroyuki; Nagatomo, Hideo; Azechi, Hiroshi

2015-06-01

A series of experiments were carried out to evaluate the energy-coupling efficiency from heating laser to a fuel core in the fast-ignition scheme of laser-driven inertial confinement fusion. Although the efficiency is determined by a wide variety of complex physics, from intense laser plasma interactions to the properties of high-energy density plasmas and the transport of relativistic electron beams (REB), here we simplify the physics by breaking down the efficiency into three measurable parameters: (i) energy conversion ratio from laser to REB, (ii) probability of collision between the REB and the fusion fuel core, and (iii) fraction of energy deposited in the fuel core from the REB. These three parameters were measured with the newly developed experimental platform designed for mimicking the plasma conditions of a realistic integrated fast-ignition experiment. The experimental results indicate that the high-energy tail of REB must be suppressed to heat the fuel core efficiently.

FY14 LLNL OMEGA Experimental Programs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heeter, R. F.; Fournier, K. B.; Baker, K.

In FY14, LLNL’s High-Energy-Density Physics (HED) and Indirect Drive Inertial Confinement Fusion (ICF-ID) programs conducted several campaigns on the OMEGA laser system and on the EP laser system, as well as campaigns that used the OMEGA and EP beams jointly. Overall these LLNL programs led 324 target shots in FY14, with 246 shots using just the OMEGA laser system, 62 shots using just the EP laser system, and 16 Joint shots using Omega and EP together. Approximately 31% of the total number of shots (62 OMEGA shots, 42 EP shots) shots supported the Indirect Drive Inertial Confinement Fusion Campaign (ICF-ID).more » The remaining 69% (200 OMEGA shots and 36 EP shots, including the 16 Joint shots) were dedicated to experiments for High- Energy-Density Physics (HED). Highlights of the various HED and ICF campaigns are summarized in the following reports.« less

FY15 LLNL OMEGA Experimental Programs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heeter, R. F.; Baker, K. L.; Barrios, M. A.

In FY15, LLNL’s High-Energy-Density Physics (HED) and Indirect Drive Inertial Confinement Fusion (ICF-ID) programs conducted several campaigns on the OMEGA laser system and on the EP laser system, as well as campaigns that used the OMEGA and EP beams jointly. Overall these LLNL programs led 468 target shots in FY15, with 315 shots using just the OMEGA laser system, 145 shots using just the EP laser system, and 8 Joint shots using Omega and EP together. Approximately 25% of the total number of shots (56 OMEGA shots and 67 EP shots, including the 8 Joint shots) supported the Indirect Drivemore » Inertial Confinement Fusion Campaign (ICF-ID). The remaining 75% (267 OMEGA shots and 86 EP shots) were dedicated to experiments for High-Energy-Density Physics (HED). Highlights of the various HED and ICF campaigns are summarized in the following reports.« less

Inertial Confinement Fusion quarterly report, January-March 1998, volume 8, number 2

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kruer, W

1998-03-31

The coupling of laser light with plasmas is one of the key physics issues for the use of high-power lasers for inertial fusion, high-energy-density physics, and scientific stockpile stewardship. The coupling physics is extremely rich and challenging, particularly in the large plasmas to be accessed on the National Ignition Facility (NIF). The coupling mechanisms span the gamut from classical inverse bremsstrahlung absorption to a variety of nonlinear optical processes. These include stimulated Raman scattering (SRS) from electron plasma waves, stimulated Brillouin scattering (SBS) from ion sound waves, resonant decay into electron plasma and ion sound waves, and laser beam filamentation.more » These processes depend on laser intensity and produce effects such as changes in the efficiency and location of the energy deposition or generation of a component of very energetic electrons, which can preheat capsules. Coupling physics issues have an extremely high leverage. The coupling models are clearly very important ingredients for detailed calculations of laser-irradiated target behavior. Improved understanding and models enable a more efficient use of laser facilities, which becomes even more important as these facilities become larger and more expensive. Advances in the understanding also allow a more timely and cost-effective identification of new applications of high-power lasers, such as for generation of high-temperature hohlraums and compact x-ray sources, or for discovery of advanced fusion schemes. Finally, the interaction of intense electromagnetic waves with ionized media is a fundamental topic of interest to numerous areas of applied science and is an excellent test bed for advancing plasma science and computational modeling of complex phenomena. This issue of the ICF Quarterly Report is dedicated to laser--plasma interactions. The eight articles present a cross section of the broad progress in understanding the key interaction issues, such as laser beam bending, spraying, and scattering, as well as scaling the Nova results to NIF.« less

A passively mode locked thulium doped fiber laser using bismuth telluride deposited multimode interference

NASA Astrophysics Data System (ADS)

Jung, M.; Lee, J.; Song, W.; Lee, Y. L.; Lee, J. H.; Shin, W.

2016-05-01

We proposed a multimode interference (MMI) fiber based saturable absorber using bismuth telluride at  ∼2 μm region. Our MMI based saturable absorber was fabricated by fusion splicing with single mode fiber and null core fiber. The MMI functioned as both wavelength fixed filter and saturable absorber. The 3 dB bandwidth and insertion loss of MMI were 42 nm and 3.4 dB at wavelength of 1958 nm, respectively. We have also reported a passively mode locked thulium doped fiber laser operating at a wavelength of 1958 nm using a multimode interference. A temporal bandwidth of  ∼46 ps was experimentally obtained at a repetition rate of 8.58 MHz.

Lead (Pb) Hohlraum: Target for Inertial Fusion Energy

PubMed Central

Ross, J. S.; Amendt, P.; Atherton, L. J.; Dunne, M.; Glenzer, S. H.; Lindl, J. D.; Meeker, D.; Moses, E. I.; Nikroo, A.; Wallace, R.

2013-01-01

Recent progress towards demonstrating inertial confinement fusion (ICF) ignition at the National Ignition Facility (NIF) has sparked wide interest in Laser Inertial Fusion Energy (LIFE) for carbon-free large-scale power generation. A LIFE-based fleet of power plants promises clean energy generation with no greenhouse gas emissions and a virtually limitless, widely available thermonuclear fuel source. For the LIFE concept to be viable, target costs must be minimized while the target material efficiency or x-ray albedo is optimized. Current ICF targets on the NIF utilize a gold or depleted uranium cylindrical radiation cavity (hohlraum) with a plastic capsule at the center that contains the deuterium and tritium fuel. Here we show a direct comparison of gold and lead hohlraums in efficiently ablating deuterium-filled plastic capsules with soft x rays. We report on lead hohlraum performance that is indistinguishable from gold, yet costing only a small fraction. PMID:23486285

Lead (Pb) hohlraum: target for inertial fusion energy.

PubMed

Ross, J S; Amendt, P; Atherton, L J; Dunne, M; Glenzer, S H; Lindl, J D; Meeker, D; Moses, E I; Nikroo, A; Wallace, R

2013-01-01

Recent progress towards demonstrating inertial confinement fusion (ICF) ignition at the National Ignition Facility (NIF) has sparked wide interest in Laser Inertial Fusion Energy (LIFE) for carbon-free large-scale power generation. A LIFE-based fleet of power plants promises clean energy generation with no greenhouse gas emissions and a virtually limitless, widely available thermonuclear fuel source. For the LIFE concept to be viable, target costs must be minimized while the target material efficiency or x-ray albedo is optimized. Current ICF targets on the NIF utilize a gold or depleted uranium cylindrical radiation cavity (hohlraum) with a plastic capsule at the center that contains the deuterium and tritium fuel. Here we show a direct comparison of gold and lead hohlraums in efficiently ablating deuterium-filled plastic capsules with soft x rays. We report on lead hohlraum performance that is indistinguishable from gold, yet costing only a small fraction.

The US ICF Ignition Program and the Inertial Fusion Program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lindl, J D; Hammel, B A; Logan, B G

2003-07-02

There has been rapid progress in inertial fusion in the past few years. This progress spans the construction of ignition facilities, a wide range of target concepts, and the pursuit of integrated programs to develop fusion energy using lasers, ion beams and z-pinches. Two ignition facilities are under construction (NIF in the U.S. and LMJ in France) and both projects are progressing toward an initial experimental capability. The LIL prototype beamline for LMJ and the first 4 beams of NIF will be available for experiments in 2003. The full 192 beam capability of NIF will be available in 2009 andmore » ignition experiments are expected to begin shortly after that time. There is steady progress in the target science and target fabrication in preparation for indirect drive ignition experiments on NIF. Advanced target designs may lead to 5-10 times more yield than initial target designs. There has also been excellent progress on the science of ion beam and z-pinch driven indirect drive targets. Excellent progress on direct-drive targets has been obtained on the Omega laser at the University of Rochester. This includes improved performance of targets with a pulse shape predicted to result in reduced hydrodynamic instability. Rochester has also obtained encouraging results from initial cryogenic implosions. There is widespread interest in the science of fast ignition because of its potential for achieving higher target gain with lower driver energy and relaxed target fabrication requirements. Researchers from Osaka have achieved outstanding implosion and heating results from the Gekko XII Petawatt facility and implosions suitable for fast ignition have been tested on the Omega laser. A broad based program to develop lasers and ions beams for IFE is under way with excellent progress in drivers, chambers, target fabrication and target injection. KrF and Diode Pumped Solid-State lasers (DPSSL) are being developed in conjunction with drywall chambers and direct drive targets. Induction accelerators for heavy ions are being developed in conjunction with thick-liquid protected wall chambers and indirect-drive targets.« less

Intense ionizing radiation from laser-induced processes in ultra-dense deuterium D(-1)

NASA Astrophysics Data System (ADS)

Olofson, Frans; Holmlid, Leif

2014-09-01

Nuclear fusion in ultra-dense deuterium D(-1) has been reported from our laboratory in a few studies using pulsed lasers with energy < 0.2 J. The direct observation of massive particles with energy 1-20 MeV u-1 is conclusive proof for fusion processes, either as a cause or as a result. Continuing the step-wise approach necessary for untangling a complex problem, the high-energy photons from the laser-induced plasma are now studied. The focus is here on the photoelectrons formed. The photons penetrating a copper foil have energy > 80 keV. The total charge created is up to 2 μC or 1 × 1013 photoelectrons per laser shot at 0.13 J pulse energy, assuming isotropic photon emission. The variation of the photoelectron current with laser intensity is faster than linear for some systems, which indicates rapid approach to volume ignition. On a permanent magnet at approximately 1 T, a laser pulse-energy threshold exists for the laser-induced processes probably due to the floating of most clusters of D(-1) in the magnetic field. This Meissner effect was reported previously.

Thick SS316 materials TIG welding development activities towards advanced fusion reactor vacuum vessel applications

NASA Astrophysics Data System (ADS)

Kumar, B. Ramesh; Gangradey, R.

2012-11-01

Advanced fusion reactors like ITER and up coming Indian DEMO devices are having challenges in terms of their materials design and fabrication procedures. The operation of these devices is having various loads like structural, thermo-mechanical and neutron irradiation effects on major systems like vacuum vessel, divertor, magnets and blanket modules. The concept of double wall vacuum vessel (VV) is proposed in view of protecting of major reactor subsystems like super conducting magnets, diagnostic systems and other critical components from high energy 14 MeV neutrons generated from fusion plasma produced by D-T reactions. The double walled vacuum vessel is used in combination with pressurized water circulation and some special grade borated steel blocks to shield these high energy neutrons effectively. The fabrication of sub components in VV are mainly used with high thickness SS materials in range of 20 mm- 60 mm of various grades based on the required protocols. The structural components of double wall vacuum vessel uses various parts like shields, ribs, shells and diagnostic vacuum ports. These components are to be developed with various welding techniques like TIG welding, Narrow gap TIG welding, Laser welding, Hybrid TIG laser welding, Electron beam welding based on requirement. In the present paper the samples of 20 mm and 40 mm thick SS 316 materials are developed with TIG welding process and their mechanical properties characterization with Tensile, Bend tests and Impact tests are carried out. In addition Vickers hardness tests and microstructural properties of Base metal, Heat Affected Zone (HAZ) and Weld Zone are done. TIG welding application with high thick SS materials in connection with vacuum vessel requirements and involved criticalities towards welding process are highlighted.

Microstructural analysis of laser weld fusion zone in Haynes 282 superalloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Osoba, L.O.; Ding, R.G.; Ojo, O.A., E-mail: ojo@cc.umanitoba.ca

Analytical electron microscopy and spectroscopy analyses of the fusion zone (FZ) microstructure in autogenous laser beam welded Haynes 282 (HY 282) superalloy were performed. The micro-segregation patterns observed in the FZ indicate that Co, Cr and Al exhibited a nearly uniform distribution between the dendrite core and interdendritic regions while Ti and Mo were rejected into the interdendritic liquid during the weld solidification. Transmission electron diffraction analysis and energy dispersive X-ray microanalysis revealed the second phase particles formed along the FZ interdendritic region to be Ti-Mo rich MC-type carbide particles. Weld FZ solidification cracking, which is sometimes associated with themore » formation of {gamma}-{gamma}' eutectic in {gamma}' precipitation strengthened nickel-base superalloys, was not observed in the HY 282 superalloy. Modified primary solidification path due to carbon addition in the newly developed superalloy is used to explain preclusion of weld FZ solidification cracking in the material. - Highlights: Black-Right-Pointing-Pointer A newly developed superalloy was welded by CO{sub 2} laser beam joining technique. Black-Right-Pointing-Pointer Electron microscopy characterization of the weld microstructure was performed. Black-Right-Pointing-Pointer Identified interdendritic microconstituents consist of MC-type carbides. Black-Right-Pointing-Pointer Modification of primary solidification path is used to explain cracking resistance.« less

Origins and Scaling of Hot-Electron Preheat in Ignition-Scale Direct-Drive Inertial Confinement Fusion Experiments.

PubMed

Rosenberg, M J; Solodov, A A; Myatt, J F; Seka, W; Michel, P; Hohenberger, M; Short, R W; Epstein, R; Regan, S P; Campbell, E M; Chapman, T; Goyon, C; Ralph, J E; Barrios, M A; Moody, J D; Bates, J W

2018-02-02

Planar laser-plasma interaction (LPI) experiments at the National Ignition Facility (NIF) have allowed access for the first time to regimes of electron density scale length (∼500 to 700  μm), electron temperature (∼3 to 5 keV), and laser intensity (6 to 16×10^{14}  W/cm^{2}) that are relevant to direct-drive inertial confinement fusion ignition. Unlike in shorter-scale-length plasmas on OMEGA, scattered-light data on the NIF show that the near-quarter-critical LPI physics is dominated by stimulated Raman scattering (SRS) rather than by two-plasmon decay (TPD). This difference in regime is explained based on absolute SRS and TPD threshold considerations. SRS sidescatter tangential to density contours and other SRS mechanisms are observed. The fraction of laser energy converted to hot electrons is ∼0.7% to 2.9%, consistent with observed levels of SRS. The intensity threshold for hot-electron production is assessed, and the use of a Si ablator slightly increases this threshold from ∼4×10^{14} to ∼6×10^{14}  W/cm^{2}. These results have significant implications for mitigation of LPI hot-electron preheat in direct-drive ignition designs.

The Quest for Fusion at the National Ignition Facility

NASA Astrophysics Data System (ADS)

Hartouni, Edward

2017-01-01

Arthur Eddington speculated in 1920 on the internal constitution of stars and described the possibility of nuclear fusion based on the then new results from special relativity and measurements of light nuclei masses. By 1929 Atkinson and Houtermans worked out the calculations for nuclear fusion in stars and initiating nuclear astrophysics. All of these sciences were pressed into service during the World War II, and the applications developed, particularly under the auspices of the Manhattan Project provided both weapons with which to wage and win that conflict, but also the possibilities to harness these applications of the nuclear processes of fission and fusion for peaceful purposes. 32 years after Eddington's speculation the United States demonstrated the application of fusion in a famous nuclear weapons test. In the following years many ideas for producing ``controlled'' fusion through inertial confinement were pursued. The invention of the laser opened up new avenues which have culminated in the National Ignition Facility, NIF. I will attempt to cover the ground between Eddington, through the Manhattan Project and provide a current status of this quest at NIF. LLNL-ABS-704367-DRAFT. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Design of welding parameters for laser welding of thin-walled stainless steel tubes using numerical simulation

NASA Astrophysics Data System (ADS)

Nagy, M.; Behúlová, M.

2017-11-01

Nowadays, the laser technology is used in a wide spectrum of applications, especially in engineering, electronics, medicine, automotive, aeronautic or military industries. In the field of mechanical engineering, the laser technology reaches the biggest increase in the automotive industry, mainly due to the introduction of automation utilizing 5-axial movements. Modelling and numerical simulation of laser welding processes has been exploited with many advantages for the investigation of physical principles and complex phenomena connected with this joining technology. The paper is focused on the application of numerical simulation to the design of welding parameters for the circumferential laser welding of thin-walled exhaust pipes from theAISI 304 steel for automotive industry. Using the developed and experimentally verified simulation model for laser welding of tubes, the influence of welding parameters including the laser velocity from 30 mm.s-1 to 60 mm.s-1 and the laser power from 500 W to 1200 W on the temperature fields and dimensions of fusion zone was investigated using the program code ANSYS. Based on obtained results, the welding schedule for the laser beam welding of thin-walled tubes from the AISI 304 steel was suggested.

Lasers '81

DOE Office of Scientific and Technical Information (OSTI.GOV)

Collins, C.B.

1982-01-01

Progress in lasers is discussed. The subjects addressed include: excimer lasers, surface spectroscopy, modern laser spectroscopy, free electron lasers, cavities and propagation, lasers in medicine, X-ray and gamma ray lasers, laser spectroscopy of small molecules and clusters, optical bistability, excitons, nonlinear optics in the X-ray and gamma ray regions, collective atomic phenomena, tunable IR lasers, far IR/submillimeter lasers, and laser-assisted collisions. Also treated are: special applications, multiphoton processes in atoms and small molecules, nuclear pumped lasers, material processing and applications, polarization, high energy lasers, laser chemistry, IR molecular lasers, laser applications of collision and dissociation phenomena, solid state laser materials,more » phase conjugation, advances in laser technology for fusion, metal vapor lasers, picosecond phenomena, laser ranging and geodesy, and laser photochemistry of complex molecules.« less

A practical nonlocal model for heat transport in magnetized laser plasmas

NASA Astrophysics Data System (ADS)

Nicolaï, Ph. D.; Feugeas, J.-L. A.; Schurtz, G. P.

2006-03-01

A model of nonlocal transport for multidimensional radiation magnetohydrodynamics codes is presented. In laser produced plasmas, it is now believed that the heat transport can be strongly modified by the nonlocal nature of the electron conduction. Other mechanisms, such as self-generated magnetic fields, may also affect the heat transport. The model described in this work, based on simplified Fokker-Planck equations aims at extending the model of G. Schurtz, Ph. Nicolaï, and M. Busquet [Phys. Plasmas 7, 4238 (2000)] to magnetized plasmas. A complete system of nonlocal equations is derived from kinetic equations with self-consistent electric and magnetic fields. These equations are analyzed and simplified in order to be implemented into large laser fusion codes and coupled to other relevant physics. The model is applied to two laser configurations that demonstrate the main features of the model and point out the nonlocal Righi-Leduc effect in a multidimensional case.

Computational Simulation of Thermal and Spattering Phenomena and Microstructure in Selective Laser Melting of Inconel 625

NASA Astrophysics Data System (ADS)

Özel, Tuğrul; Arısoy, Yiğit M.; Criales, Luis E.

Computational modelling of Laser Powder Bed Fusion (L-PBF) processes such as Selective laser Melting (SLM) can reveal information that is hard to obtain or unobtainable by in-situ experimental measurements. A 3D thermal field that is not visible by the thermal camera can be obtained by solving the 3D heat transfer problem. Furthermore, microstructural modelling can be used to predict the quality and mechanical properties of the product. In this paper, a nonlinear 3D Finite Element Method based computational code is developed to simulate the SLM process with different process parameters such as laser power and scan velocity. The code is further improved by utilizing an in-situ thermal camera recording to predict spattering which is in turn included as a stochastic heat loss. Then, thermal gradients extracted from the simulations applied to predict growth directions in the resulting microstructure.

Formation of carbon allotrope aerosol by colliding plasmas in an inertial fusion reactor

NASA Astrophysics Data System (ADS)

Hirooka, Y.; Sato, H.; Ishihara, K.; Yabuuchi, T.; Tanaka, K. A.

2014-02-01

Along with repeated implosions, the interior of an inertial fusion target chamber is exposed to short pulses of high-energy x-ray, unburned DT-fuel particles, He-ash and pellet debris. As a result, chamber wall materials are subjected to ablation, emitting particles in the plasma state. Ablated particles will either be re-deposited elsewhere or collide with each other, perhaps in the centre-of-symmetry region of the chamber volume. Colliding ablation plasma particles can lead to the formation of clusters to grow into aerosol, possibly floating thereafter, which can deteriorate the subsequent implosion performance via laser scattering, etc. In a laboratory-scale YAG laser setup, the formation of nano-scale aerosol has been demonstrated in vacuum at irradiation power densities of the orders of 108-10 W cm-2 at 10 Hz, each 6 ns long, simulating the high-repetition rate inertial fusion reactor situation. Interestingly, carbon aerosol formation has been observed in the form of fullerene onion, nano- and micro-tubes when laser-ablated plasma plumes of carbon collide with each other. In contrast, colliding plasma plumes of metals tend to generate aerosol in the form of droplets under identical laser irradiation conditions. An atomic and molecular reaction model is proposed to interpret the process of carbon allotrope aerosol formation.

Production of plasmas by long-wavelength lasers

DOEpatents

Dawson, J.M.

1973-10-01

A long-wavelength laser system for heating low-density plasma to high temperatures is described. In one embodiment, means are provided for repeatedly receiving and transmitting long-wavelength laser light in successive stages to form a laser-light beam path that repeatedly intersects with the equilibrium axis of a magnetically confined toroidal plasma column for interacting the laser light with the plasma for providing controlled thermonuclear fusion. Embodiments for heating specific linear plasmas are also provided. (Official Gazette)

Raman Sidescattering in Laser-Produced Plasmas.

DTIC Science & Technology

1984-12-27

MENYUK AND N. M. EL-SIRAGY Labomtyjb Plasma and Fusion Energy Studies -~ University of Maryland College Park, MD 20 742 LnW. M. MANHEIMER2 Plasma...NOTATION *Laboratory for Plasma and Fusion Energy Studies, Univ. of Maryland, College Park, MD 20742 **Permanent Address: Physics Dept., Univ. of Tanta

Fusion of Terrestrial and Airborne Laser Data for 3D modeling Applications

NASA Astrophysics Data System (ADS)

Mohammed, Hani Mahmoud

This thesis deals with the 3D modeling phase of the as-built large BIM projects. Among several means of BIM data capturing, such as photogrammetric or range tools, laser scanners have been one of the most efficient and practical tool for a long time. They can generate point clouds with high resolution for 3D models that meet nowadays' market demands. The current 3D modeling projects of as-built BIMs are mainly focused on using one type of laser scanner data, such as Airborne or Terrestrial. According to the literatures, no significant (few) efforts were made towards the fusion of heterogeneous laser scanner data despite its importance. The importance of the fusion of heterogeneous data arises from the fact that no single type of laser data can provide all the information about BIM, especially for large BIM projects that are existing on a large area, such as university buildings, or Heritage places. Terrestrial laser scanners are able to map facades of buildings and other terrestrial objects. However, they lack the ability to map roofs or higher parts in the BIM project. Airborne laser scanner on the other hand, can map roofs of the buildings efficiently and can map only small part of the facades. Short range laser scanners can map the interiors of the BIM projects, while long range scanners are used for mapping wide exterior areas in BIM projects. In this thesis the long range laser scanner data obtained in the Stop-and-Go mapping mode, the short range laser scanner data, obtained in a fully static mapping mode, and the airborne laser data are all fused together to bring a complete effective solution for a large BIM project. Working towards the 3D modeling of BIM projects, the thesis framework starts with the registration of the data, where a new fast automatic registration algorithm were developed. The next step is to recognize the different objects in the BIM project (classification), and obtain 3D models for the buildings. The last step is the development of an occlusion removal algorithm to efficiently retain parts of the buildings occluded by surrounding objects such as trees, vehicles, or street poles.

High coupling efficiency of foam spherical hohlraum driven by 2ω laser light

NASA Astrophysics Data System (ADS)

Chen, Yao-Hua; Lan, Ke; Zheng, Wanguo; Campbell, E. M.

2018-02-01

The majority of solid state laser facilities built for laser fusion research irradiate targets with third harmonic light (0.35 μm) up-converted from the fundamental Nd wavelength at 1.05 μm. The motivation for this choice of wavelength is improved laser-plasma coupling. Significant disadvantages to this choice of wavelength are the reduced damage threshold of optical components and the efficiency of energy conversion to third harmonic light. Both these issues are significantly improved if second harmonic (0.53 μm) radiation is used, but theory and experiments have shown lower optical to x-ray energy conversion efficiency and increased levels of laser-plasma instabilities, resulting in reduced laser-target coupling. In this letter, we propose to use a 0.53 μm laser for the laser ignition facilities and use a low density foam wall to increase the coupling efficiency from the laser to the capsule and present two-dimensional radiation-hydrodynamic simulations of 0.53 μm laser light irradiating an octahedral-spherical hohlraum with a low density foam wall. The simulations show that the reduced optical depth of the foam wall leads to an increased laser-light conversion into thermal x-rays and about 10% higher radiation flux on the capsule than that achieved with 0.35 μm light irradiating a solid density wall commonly used in laser indirect drive fusion research. The details of the simulations and their implications and suggestions for wavelength scaling coupled with innovative hohlraum designs will be discussed.

Spot-shadowing optimization to mitigate damage growth in a high-energy-laser amplifier chain.

PubMed

Bahk, Seung-Whan; Zuegel, Jonathan D; Fienup, James R; Widmayer, C Clay; Heebner, John

2008-12-10

A spot-shadowing technique to mitigate damage growth in a high-energy laser is studied. Its goal is to minimize the energy loss and undesirable hot spots in intermediate planes of the laser. A nonlinear optimization algorithm solves for the complex fields required to mitigate damage growth in the National Ignition Facility amplifier chain. The method is generally applicable to any large fusion laser.

Non-critical phase-matching fourth harmonic generation of a 1053-nm laser in an ADP crystal

PubMed Central

Ji, Shaohua; Wang, Fang; Zhu, Lili; Xu, Xinguang; Wang, Zhengping; Sun, Xun

2013-01-01

In current inertial confinement fusion (ICF) facilities, KDP and DKDP crystals are the second harmonic generation (SHG) and third harmonic generation (THG) materials for the Nd:glass laser (1053 nm). Based on the trend for the development of short wavelengths for ICF driving lasers, technical solutions for fourth harmonic generation (FHG) will undoubtedly attract more and more attention. In this paper, the rapid growth of an ADP crystal and non-critical phase-matching (NCPM) FHG of a 1053-nm laser using an ADP crystal are reported. The NCPM temperature is 33.7°C. The conversion efficiency from 526 to 263 nm is 70%, and the angular acceptance range is 55.4 mrad; these results are superior to those for the DKDP crystals. This research has shown that ADP crystals will be a competitive candidate in future ICF facilities when the utilisation of high-energy, high-efficiency UV lasers at wavelengths shorter than the present 351 nm is of interest. PMID:23549389

Non-critical phase-matching fourth harmonic generation of a 1053-nm laser in an ADP crystal.

PubMed

Ji, Shaohua; Wang, Fang; Zhu, Lili; Xu, Xinguang; Wang, Zhengping; Sun, Xun

2013-01-01

In current inertial confinement fusion (ICF) facilities, KDP and DKDP crystals are the second harmonic generation (SHG) and third harmonic generation (THG) materials for the Nd:glass laser (1053 nm). Based on the trend for the development of short wavelengths for ICF driving lasers, technical solutions for fourth harmonic generation (FHG) will undoubtedly attract more and more attention. In this paper, the rapid growth of an ADP crystal and non-critical phase-matching (NCPM) FHG of a 1053-nm laser using an ADP crystal are reported. The NCPM temperature is 33.7°C. The conversion efficiency from 526 to 263 nm is 70%, and the angular acceptance range is 55.4 mrad; these results are superior to those for the DKDP crystals. This research has shown that ADP crystals will be a competitive candidate in future ICF facilities when the utilisation of high-energy, high-efficiency UV lasers at wavelengths shorter than the present 351 nm is of interest.

Spatial filter with volume gratings for high-peak-power multistage laser amplifiers

NASA Astrophysics Data System (ADS)

Tan, Yi-zhou; Yang, Yi-sheng; Zheng, Guang-wei; Shen, Ben-jian; Pan, Heng-yue; Liu, Li

2010-08-01

The regular spatial filters comprised of lens and pinhole are essential component in high power laser systems, such as lasers for inertial confinement fusion, nonlinear optical technology and directed-energy weapon. On the other hand the pinhole is treated as a bottleneck of high power laser due to harmful plasma created by the focusing beam. In this paper we present a spatial filter based on angular selectivity of Bragg diffraction grating to avoid the harmful focusing effect in the traditional pinhole filter. A spatial filter consisted of volume phase gratings in two-pass amplifier cavity were reported. Two-dimensional filter was proposed by using single Pi-phase-shifted Bragg grating, numerical simulation results shown that its angular spectrum bandwidth can be less than 160urad. The angular selectivity of photo-thermorefractive glass and RUGATE film filters, construction stability, thermal stability and the effects of misalignments of gratings on the diffraction efficiencies under high-pulse-energy laser operating condition are discussed.

Dynamics of Laser-Driven Shock Waves in Solid Targets

NASA Astrophysics Data System (ADS)

Aglitskiy, Y.; Karasik, M.; Velikovich, A. L.; Serlin, V.; Weaver, J.; Schmitt, A. J.; Obenschain, S. P.; Grun, J.; Metzler, N.; Zalesak, S. T.; Gardner, J. H.; Oh, J.; Harding, E. C.

2009-11-01

Accurate shock timing is a key issue of both indirect- and direct-drive laser fusions. The experiments on the Nike laser at NRL presented here were made possible by improvements in the imaging capability of our monochromatic x-ray diagnostics based on Bragg reflection from spherically curved crystals. Side-on imaging implemented on Nike makes it possible to observe dynamics of the shock wave and ablation front in laser-driven solid targets. We can choose to observe a sequence of 2D images or a continuous time evolution of an image resolved in one spatial dimension. A sequence of 300 ps snapshots taken using vanadium backlighter at 5.2 keV reveals propagation of a shock wave in a solid plastic target. The shape of the shock wave reflects the intensity distribution in the Nike beam. The streak records with continuous time resolution show the x-t trajectory of a laser-driven shock wave in a 10% solid density DVB foam.

Hollow screw-like drill in plasma using an intense Laguerre–Gaussian laser

PubMed Central

Wang, Wenpeng; Shen, Baifei; Zhang, Xiaomei; Zhang, Lingang; Shi, Yin; Xu, Zhizhan

2015-01-01

With the development of ultra-intense laser technology, MeV ions can be obtained from laser–foil interactions in the laboratory. These energetic ion beams can be applied in fast ignition for inertial confinement fusion, medical therapy, and proton imaging. However, these ions are mainly accelerated in the laser propagation direction. Ion acceleration in an azimuthal orientation was scarcely studied. In this research, a doughnut Laguerre–Gaussian (LG) laser is used for the first time to examine laser–plasma interaction in the relativistic intensity regime in three-dimensional particle-in-cell simulations. Studies have shown that a novel rotation of the plasma is produced from the hollow screw-like drill of an mode laser. The angular momentum of particles in the longitudinal direction produced by the LG laser is enhanced compared with that produced by the usual laser pulses, such as linearly and circularly polarized Gaussian pulses. Moreover, the particles (including electrons and ions) can be trapped and uniformly compressed in the dark central minimum of the doughnut LG pulse. The hollow-structured LG laser has potential applications in the generation of x-rays with orbital angular momentum, plasma accelerators, fast ignition for inertial confinement fusion, and pulsars in the astrophysical environment. PMID:25651780

Characterizing the Effect of Laser Power on Laser Metal Deposited Titanium Alloy and Boron Carbide

NASA Astrophysics Data System (ADS)

Akinlabi, E. T.; Erinosho, M. F.

2017-11-01

Titanium alloy has gained acceptance in the aerospace, marine, chemical, and other related industries due to its excellent combination of mechanical and corrosion properties. In order to augment its properties, a hard ceramic, boron carbide has been laser cladded with it at varying laser powers between 0.8 and 2.4 kW. This paper presents the effect of laser power on the laser deposited Ti6Al4V-B4C composites through the evolving microstructures and microhardness. The microstructures of the composites exhibit the formation of α-Ti phase and β-Ti phase and were elongated towards the heat affected zone. These phases were terminated at the fusion zone and globular microstructures were found growing epitaxially just immediately after the fusion zone. Good bondings were formed in all the deposited composites. Sample A1 deposited at a laser power of 0.8 kW and scanning speed of 1 m/min exhibits the highest hardness of HV 432 ± 27, while sample A4 deposited at a laser power of 2.0 kW and scanning speed of 1 m/min displays the lowest hardness of HV 360 ± 18. From the hardness results obtained, ceramic B4C has improved the mechanical properties of the primary alloy.

Optical coatings on laser crystals for HiPER project

NASA Astrophysics Data System (ADS)

Oulehla, Jindrich; Pokorný, Pavel; Lazar, Josef

2011-12-01

In this contribution we present a technology for deposition of interference coatings for optical components designed to operate as active media in power pulsed lasers. The aim of the technology is to prepare crystals for lasers for the HiPER project (High Power laser Energy Research facility) which should demonstrate the feasibility of laser driven fusion as a future energy source. Diode pumped solid state lasers (DPSSL) are the most likely option for fusion ignition. The choice of the material for the lasers' active medium is critical. Some of the most important properties include the ability to be antireflection coated to reduce the energy losses and increase the overall efficiency. This contribution deals with some of the materials considered to be candidates for slabs serving as the active medium of the DPSSLs. We tested Yb:YAG and Yb:CaF2 samples. As large amounts of heat need to be dissipated during laser operation, cryogenic cooling is necessary. Appropriate coating materials and techniques need to be chosen. Therefore differences between available coating techniques are investigated in terms of adhesion, enduring of stress from temperature shocks, etc. Coated samples were placed into cryogenic environment in order to simulate conditions similar to those in real life operation. Optical microscopy was used for coating investigation after the conducted experiments.

AR coatings on laser crystals for HiPER project

NASA Astrophysics Data System (ADS)

Oulehla, Jindřich; Pokorný, Pavel

2010-08-01

In this contribution we present a technology for deposition of interference coatings for optical components designed to operate as active media in power pulsed lasers. The aim of the technology is to prepare crystals for lasers for the HiPER project (High Power laser Energy Research) which should demonstrate the feasibility of laser driven fusion as a future energy source. Diode pumped solid state lasers (DPSSL) are the most likely option for fusion ignition. The choice of material for the lasers active medium is critical. Some of the most important properties include the ability to be antireflection coated to reduce the energy losses and increase the overall efficiency. This contribution deals with some of the materials considered to be candidates for slabs serving as the active medium of the DPSSLs. We tested Yb:YAG, Yb:CaF2 samples. As large amounts of heat need to be dissipated during laser operation, cryogenic cooling is necessary. Appropriate coating materials and techniques need to be chosen. Therefore differences between available coating techniques are investigated in terms of adhesion, enduring of stress resulting from temperature shocks, etc. Coated samples were placed into cryogenic environment in order to simulate conditions similar to those in real life operation. Optical microscopy was used for coating investigation after the conducted experiments.

Note: Neutron bang time diagnostic system on Shenguang-III prototype

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tang, Qi; Chen, Jiabin; Liu, Zhongjie

A neutron bang time (NBT) diagnostic system has been implemented on Shenguang-III prototype. The bang time diagnostic system is based on a sensitive fusion neutron detector, which consists of a plastic scintillator and a micro-channel plate photomultiplier tube (PMT). An optical fiber bundle is used to couple the scintillator and the PMT. The bang time system is able to measure bang time above a neutron yield of 10{sup 7}. Bang times and start time of laser were related by probing x-ray pulses produced by 200 ps laser irradiating golden targets. Timing accuracy of the NBT is better than 60 ps.

Dense range map reconstruction from a versatile robotic sensor system with an active trinocular vision and a passive binocular vision.

PubMed

Kim, Min Young; Lee, Hyunkee; Cho, Hyungsuck

2008-04-10

One major research issue associated with 3D perception by robotic systems is the creation of efficient sensor systems that can generate dense range maps reliably. A visual sensor system for robotic applications is developed that is inherently equipped with two types of sensor, an active trinocular vision and a passive stereo vision. Unlike in conventional active vision systems that use a large number of images with variations of projected patterns for dense range map acquisition or from conventional passive vision systems that work well on specific environments with sufficient feature information, a cooperative bidirectional sensor fusion method for this visual sensor system enables us to acquire a reliable dense range map using active and passive information simultaneously. The fusion algorithms are composed of two parts, one in which the passive stereo vision helps active vision and the other in which the active trinocular vision helps the passive one. The first part matches the laser patterns in stereo laser images with the help of intensity images; the second part utilizes an information fusion technique using the dynamic programming method in which image regions between laser patterns are matched pixel-by-pixel with help of the fusion results obtained in the first part. To determine how the proposed sensor system and fusion algorithms can work in real applications, the sensor system is implemented on a robotic system, and the proposed algorithms are applied. A series of experimental tests is performed for a variety of configurations of robot and environments. The performance of the sensor system is discussed in detail.

Laser-driven fusion reactor

DOEpatents

Hedstrom, J.C.

1973-10-01

A laser-driven fusion reactor consisting of concentric spherical vessels in which the thermonuclear energy is derived from a deuterium-tritium (D + T) burn within a pellet'', located at the center of the vessels and initiated by a laser pulse. The resulting alpha -particle energy and a small fraction of the neutron energy are deposited within the pellet; this pellet energy is eventually transformed into sensible heat of lithium in a condenser outside the vessels. The remaining neutron energy is dissipated in a lithium blanket, located within the concentric vessels, where the fuel ingredient, tritium, is also produced. The heat content of the blanket and of the condenser lithium is eventually transferred to a conventional thermodynamic plant where the thermal energy is converted to electrical energy in a steam Rankine cycle. (Official Gazette)

Compression of magnetized target in the magneto-inertial fusion

NASA Astrophysics Data System (ADS)

Kuzenov, V. V.

2017-12-01

This paper presents a mathematical model, numerical method and results of the computer analysis of the compression process and the energy transfer in the target plasma, used in magneto-inertial fusion. The computer simulation of the compression process of magnetized cylindrical target by high-power laser pulse is presented.

Comparative Evaluation of Effects of Laser Modalities on Shear Bond Strengths of Veneering Porcelains to Laser Sintered Substructures: An In Vitro Study.

PubMed

Gorler, Oguzhan; Saygin, Aysegul Goze

2017-06-01

Laser modalities and direct metal laser sintering (DMLS) have a potential to enhance micromechanical bonding between dental super- and infrastructures. However, the effect of different manufacturing methods on the metal-ceramic bond strength needs further evaluation. We investigated the effect of surface treatment with Er:YAG, Nd:YAG, and Ho:YAG lasers on the shear bond strength (SBS) of high-fusion dental porcelains (Vita and G-Ceram) to infrastructures prepared with DMLS in vitro settings. Study specimens (n = 128) were randomly divided into study subsets (n = 8), considering treatment types applied on the surface of infrastructures, including sandblasting and selected laser modalities; infrastructure types as direct laser sintered (DLS) and Ni-Cr based; and superstructure porcelains as Vita and G-Ceram. The SBS test was performed to assess the effectiveness of surface modifications that were also examined with a stereo microscope. Considering laser procedure types, the highest SBS values were obtained by Er:YAG laser, followed by, with a decreasing efficiency, Ho:YAG laser and sandblasting procedures, and Nd:YAG laser procedure (p < 0.05). Nd:YAG laser decreases the bonding of Vita and G-Ceram in all the infrastructures compared with sandblasting. Considering porcelains, the highest SBS values were obtained by Vita (p < 0.05). Considering infrastructures, the highest SBS values were obtained by DMLS procedure (p < 0.05). The laser procedures caused surface irregularities as revealed by the stereo microscopic examination. In current experimental settings, Er:YAG laser applied to DLS infrastructure veneered with Vita porcelain increases bonding strength more distinctly, and Nd:YAG laser applied to Ni-Cr-based infrastructure veneered with G-Ceram porcelain alters bonding strength unfavorably.

Co-Registration of DSMs Generated by Uav and Terrestrial Laser Scanning Systems

NASA Astrophysics Data System (ADS)

Ancil Persad, Ravi; Armenakis, Costas

2016-06-01

An approach for the co-registration of Digital Surface Models (DSMs) derived from Unmanned Aerial Vehicles (UAVs) and Terrestrial Laser Scanners (TLS) is proposed. Specifically, a wavelet-based feature descriptor for matching surface keypoints on the 2.5D DSMs is developed. DSMs are useful in wide-scope of various applications such as 3D building modelling and reconstruction, cultural heritage, urban and environmental planning, aircraft navigation/path routing, accident and crime scene reconstruction, mining as well as, topographic map revision and change detection. For these listed applications, it is not uncommon that there will be a need for automatically aligning multi-temporal DSMs which may have been acquired from multiple sensors, with different specifications over a period of time, and may have various overlaps. Terrestrial laser scanners usually capture urban facades in an accurate manner; however this is not the case for building roof structures. On the other hand, vertical photography from UAVs can capture the roofs. Therefore, the automatic fusion of UAV and laser-scanning based DSMs is addressed here as it serves various geospatial applications.

Human-technology interaction for standoff IED detection

NASA Astrophysics Data System (ADS)

Zhang, Evan; Zou, Yiyang; Zachrich, Liping; Fulton, Jack

2011-03-01

IEDs kill our soldiers and innocent people every day. Lessons learned from Iraq and Afghanistan clearly indicated that IEDs cannot be detected/defeated by technology alone; human-technology interaction must be engaged. In most cases, eye is the best detector, brain is the best computer, and technologies are tools, they must be used by human being properly then can achieve full functionality. In this paper, a UV Raman/fluorescence, CCD and LWIR 3 sensor fusion system for standoff IED detection and a handheld fusion system for close range IED detection are developed and demonstrated. We must train solders using their eyes or CCD/LWIR cameras to do wide area search while on the move to find small suspected area first then use the spectrometer because the laser spot is too small, to scan a one-mile long and 2-meter wide road needs 185 days although our fusion system can detect the IED in 30m with 1s interrogating time. Even if the small suspected area (e.g., 0.5mx0.5m) is found, human eyes still cannot detect the IED, soldiers must use or interact with the technology - laser based spectrometer to scan the area then they are able to detect and identify the IED in 10 minutes not 185 days. Therefore, the human-technology interaction approach will be the best solution for IED detection.

Effect of different filler wires on weld formation for fiber laser welding 6A02 Aluminum alloy

NASA Astrophysics Data System (ADS)

Xu, F.; Chen, L.; Lu, W.; He, E. G.

2017-12-01

6A02 aluminum alloy was welded by fibre laser welding with two different filler wires (ER4043 and ER5356). The weld apperance, microstructure and mechanical properties were analysed. The results show the welding course with ER4043 is more stable than that with ER5356, and the welding spatters of the former are smaller than that of the latter. The microsturtrue of the weld zone, including columnar-grains near the fusion zone and mixed microstructures (columnar grains and equiaxed grains) in the weld center zone, is finer with ER5356 than that with ER4043. So the average microhardness value of the former is higher than the latter. A great number of low melting point eutectic phases disperse in grains boundary. Due to the eutectic phases distributing more in two zones (overheat zone near the fusion zone and the weld center zone) than other zones, the welded joints have these two low hardness and weak strength zones. The ultimate strength and the elongations after fracture of the welded joints with ER4043 are lower than that with ER5356 slihgtly. However, the former are improved obviously and higher than the latter after heat treatment. The tensile properties of all joints can reach to the base material level. And the tensile fractures always occur near the fusion zone.

The influence of the Q-switched and free-running Er:YAG laser beam characteristics on the ablation of root canal dentine

NASA Astrophysics Data System (ADS)

Papagiakoumou, Eirini; Papadopoulos, Dimitrios N.; Khabbaz, Marouan G.; Makropoulou, Mersini I.; Serafetinides, Alexander A.

2004-06-01

Laser based dental treatment is attractive to many researchers. Lasers in the 3 μm region, as the Er:YAG, are suitable especially for endodontic applications. In this study a pulsed free-running and Q-switched laser was used for the ablation experiments of root canal dentine. The laser beam was either directly focused on the dental tissue or delivered to it through an infrared fiber. For different spatial beam distributions, energies, number of pulses and both laser operations the quality characteristics (crater's shape formation, ablation efficiency and surface characteristics modification) were evaluated using scanning electron microscopy (SEM). The craters produced, generally, reflect the relevant beam profile. Inhomogeneous spatial beam profiles and short pulse duration result in cracks formation and lower tissue removal efficiency, while longer pulse durations cause hard dentine fusion. Any beam profile modification, due to laser characteristics variations and the specific delivering system properties, is directly reflected in the ablation crater shape and the tissue removal efficiency. Therefore, the laser parameters, as fluence, pulse repetition rate and number of pulses, have to be carefully adjusted in relation to the desirable result.

Interaction of laser beams with magnetized substance in a strong magnetic field

NASA Astrophysics Data System (ADS)

Kuzenov, V. V.

2018-03-01

Laser-driven magneto-inertial fusion assumed plasma and magnetic flux compression by quasisymmetric laser-driven implosion of magnetized target. We develop a 2D radiation magnetohydrodynamic code and a formulation for the one-fluid two-temperature equations for simulating compressible non-equilibrium magnetized target plasma. Laser system with pulse radiation with 10 ns duration is considered for numerical experiments. A numerical study of a scheme of magnetized laser-driven implosion in the external magnetic field is carried out.

Neodymium:yttrium-aluminum-garnet laser fusion of endarterectomy flaps.

PubMed

Humphrey, P W; Slocum, M M; Loy, T S; Silver, D

1995-07-01

This study evaluated the efficacy of neodymium:yttrium-aluminum-garnet laser welding of flaps in canine arteries and in securing the distal flap during human carotid endarterectomy. Endarterectomy flaps were created in both common carotid and both common femoral arteries in 12 dogs. The flaps were repaired with either the neodymium:yttrium-aluminum-garnet laser or with 6-0 polypropylene sutures. The arteries were removed after duplex scanning at either 7 or 28 days. Eighteen high carotid endarterectomy flaps in 16 patients have been subsequently secured with the laser welding technique. Laser repairs (125 +/- 19 joule) of the canine arteries were completed more quickly than suture repairs (mean 25 seconds vs 135 seconds, respectively; p < 0.04). Duplex ultrasonography revealed no discernable differences between the two groups of arteries. Arteries studied at 7 days revealed three microscopic flaps (two suture, one laser), more subintimal fibroblastic proliferation in suture than laser-repaired carotid arteries (3: 1, p = 0.0530), and similar amounts of inflammation in suture- and laser-repaired arteries. Arteries studied at 28 days revealed one microscopic intimal flap (suture-repaired); equal fibroblastic and inflammatory responses in suture- and laser-repaired vessels; and no evidence of laser thermal injury. Eighteen carotid endarterectomy flaps have been successfully fused with no immediate or long-term complications in 16 patients (follow-up of 0 to 24 months). Laser fusion appears to be a safe and effective method for securing distal carotid endarterectomy flaps.

Design of continuous surface-relief phase plates by surface-based simulated annealing to achieve control of focal-plane irradiance

NASA Astrophysics Data System (ADS)

Lin, Y.; Kessler, T. J.; Lawrence, G. N.

1996-10-01

High-performance phase plates are of vital concern for controlling the far-field irradiance of laser-fusion systems. Several designs for solving this difficult problem have been reported in Optics Letters [e. g., S. N. Dixit et al., Opt. Lett. 19, 417 (1994)]. We report a surface-based form of simulated annealing that significantly improves the irradiance control while eliminating the high-scatter problems that have plagued other methods.

Optically sectioned in vivo imaging with speckle illumination HiLo microscopy

PubMed Central

Lim, Daryl; Ford, Tim N.; Chu, Kengyeh K.; Mertz, Jerome

2011-01-01

We present a simple wide-field imaging technique, called HiLo microscopy, that is capable of producing optically sectioned images in real time, comparable in quality to confocal laser scanning microscopy. The technique is based on the fusion of two raw images, one acquired with speckle illumination and another with standard uniform illumination. The fusion can be numerically adjusted, using a single parameter, to produce optically sectioned images of varying thicknesses with the same raw data. Direct comparison between our HiLo microscope and a commercial confocal laser scanning microscope is made on the basis of sectioning strength and imaging performance. Specifically, we show that HiLo and confocal 3-D imaging of a GFP-labeled mouse brain hippocampus are comparable in quality. Moreover, HiLo microscopy is capable of faster, near video rate imaging over larger fields of view than attainable with standard confocal microscopes. The goal of this paper is to advertise the simplicity, robustness, and versatility of HiLo microscopy, which we highlight with in vivo imaging of common model organisms including planaria, C. elegans, and zebrafish. PMID:21280920

Optically sectioned in vivo imaging with speckle illumination HiLo microscopy.

PubMed

Lim, Daryl; Ford, Tim N; Chu, Kengyeh K; Mertz, Jerome

2011-01-01

We present a simple wide-field imaging technique, called HiLo microscopy, that is capable of producing optically sectioned images in real time, comparable in quality to confocal laser scanning microscopy. The technique is based on the fusion of two raw images, one acquired with speckle illumination and another with standard uniform illumination. The fusion can be numerically adjusted, using a single parameter, to produce optically sectioned images of varying thicknesses with the same raw data. Direct comparison between our HiLo microscope and a commercial confocal laser scanning microscope is made on the basis of sectioning strength and imaging performance. Specifically, we show that HiLo and confocal 3-D imaging of a GFP-labeled mouse brain hippocampus are comparable in quality. Moreover, HiLo microscopy is capable of faster, near video rate imaging over larger fields of view than attainable with standard confocal microscopes. The goal of this paper is to advertise the simplicity, robustness, and versatility of HiLo microscopy, which we highlight with in vivo imaging of common model organisms including planaria, C. elegans, and zebrafish.

Optically sectioned in vivo imaging with speckle illumination HiLo microscopy

NASA Astrophysics Data System (ADS)

Lim, Daryl; Ford, Tim N.; Chu, Kengyeh K.; Mertz, Jerome

2011-01-01

We present a simple wide-field imaging technique, called HiLo microscopy, that is capable of producing optically sectioned images in real time, comparable in quality to confocal laser scanning microscopy. The technique is based on the fusion of two raw images, one acquired with speckle illumination and another with standard uniform illumination. The fusion can be numerically adjusted, using a single parameter, to produce optically sectioned images of varying thicknesses with the same raw data. Direct comparison between our HiLo microscope and a commercial confocal laser scanning microscope is made on the basis of sectioning strength and imaging performance. Specifically, we show that HiLo and confocal 3-D imaging of a GFP-labeled mouse brain hippocampus are comparable in quality. Moreover, HiLo microscopy is capable of faster, near video rate imaging over larger fields of view than attainable with standard confocal microscopes. The goal of this paper is to advertise the simplicity, robustness, and versatility of HiLo microscopy, which we highlight with in vivo imaging of common model organisms including planaria, C. elegans, and zebrafish.

Modeling the Removal of Xenon from Lithium Hydrate with Aspen HYSYS

NASA Astrophysics Data System (ADS)

Efthimion, Phillip; Gentile, Charles

2011-10-01

The Laser Inertial Fusion Engine (LIFE) project mission is to provide a long-term, carbon-free source of sustainable energy, in the form of electricity. A conceptual xenon removal system has been modeled with the aid of Aspen HYSYS, a chemical process simulator. Aspen HYSYS provides excellent capability to model chemical flow processes, which generates outputs which includes specific variables such as temperature, pressure, and molar flow. The system is designed to strip out hydrogen isotopes deuterium and tritium. The base design bubbles plasma exhaust laden with x filled with liquid helium. The system separates the xenon from the hydrogen, deuterium, and tritium with a lithium hydrate and a lithium bubbler. After the removal of the hydrogen and its isotopes, the xenon is then purified by way of the process of cryogenic distillation. The pure hydrogen, deuterium, and tritium are then sent to the isotope separation system (ISS). The removal of xenon is an integral part of the laser inertial fusion engine and Aspen HYSYS is an excellent tool to calculate how to create pure xenon.

Thermal model for optimization of vascular laser tissue soldering.

PubMed

Bogni, Serge; Stumpp, Oliver; Reinert, Michael; Frenz, Martin

2010-06-01

Laser tissue soldering (LTS) is a promising technique for tissue fusion based on a heat-denaturation process of proteins. Thermal damage of the fused tissue during the laser procedure has always been an important and challenging problem. Particularly in LTS of arterial blood vessels strong heating of the endothelium should be avoided to minimize the risk of thrombosis. A precise knowledge of the temperature distribution within the vessel wall during laser irradiation is inevitable. The authors developed a finite element model (FEM) to simulate the temperature distribution within blood vessels during LTS. Temperature measurements were used to verify and calibrate the model. Different parameters such as laser power, solder absorption coefficient, thickness of the solder layer, cooling of the vessel and continuous vs. pulsed energy deposition were tested to elucidate their impact on the temperature distribution within the soldering joint in order to reduce the amount of further animal experiments. A pulsed irradiation with high laser power and high absorbing solder yields the best results. (c) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Experimental and simulated ultrasonic characterization of complex damage in fused silica.

PubMed

Martin, L Peter; Chambers, David H; Thomas, Graham H

2002-02-01

The growth of a laser-induced, surface damage site in a fused silica window was monitored by the ultrasonic pulse-echo technique. The laser damage was grown using 12-ns pulses of 1.053-microm wavelength light at a fluence of approximately 27 J/cm2. The ultrasonic data were acquired after each pulse of the laser beam for 19 pulses. In addition, optical images of the surface and subsurface damage shape were recorded after each pulse of the laser. The ultrasonic signal amplitude exhibited variations with the damage size, which were attributed to the subsurface morphology of the damage site. A mechanism for the observed ultrasonic data based on the interaction of the ultrasound with cracks radiating from the damage site was tested using two-dimensional numerical simulations. The simulated results exhibit qualitatively similar characteristics to the experimental data and demonstrate the usefulness of numerical simulation as an aid for ultrasonic signal interpretation. The observed sensitivity to subsurface morphology makes the ultrasonic methodology a promising tool for monitoring laser damage in large aperture laser optics used in fusion energy research.

Multi-wavelength laser from dye-doped cholesteric polymer films.

PubMed

Huang, Yuhua; Wu, Shin-Tson

2010-12-20

A multi-wavelength laser is demonstrated using a dye-doped cholesteric polymer film whose reflection bandwidth is broadened with several oscillations. Due to the abrupt change of the density of state between oscillation peak and valley, each oscillation functions as a photonic band gap for generating a laser wavelength under the excitation of a pumping laser. As a result, a multiple wavelength laser is generated. Results indicate that the dye-doped cholesteric liquid crystal polymer film is a good candidate for fabricating broadband lasers such as white light lasers. Potential applications include experimental testing of laser materials, identification markers, information displays, and inertial confinement laser fusion.

Theory of Skin Depth Interaction of Lasers with Plasmas

DTIC Science & Technology

2003-07-20

laser plasma interaction, Czechoslovak J. Physics, 52, Suppl. D (CD No.7), (2002) D349 [6] J.L Nuckolls and L. Wood, Future of Inertial Fusion Energy , Preprint UCRL-JC-149860 (September 4, 2002) www.llnl.gov/tid/ Library..html 224

Laser powder-bed fusion additive manufacturing: Physics of complex melt flow and formation mechanisms of pores, spatter, and denudation zones

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khairallah, Saad A.; Anderson, Andrew T.; Rubenchik, Alexander

Our study demonstrates the significant effect of the recoil pressure and Marangoni convection in laser powder bed fusion (L-PBF) of 316L stainless steel. A three-dimensional high fidelity powder-scale model reveals how the strong dynamical melt flow generates pore defects, material spattering (sparking), and denudation zones. The melt track is divided into three sections: a topological depression, a transition and a tail region, each being the location of specific physical effects. The inclusion of laser ray-tracing energy deposition in the powder-scale model improves over traditional volumetric energy deposition. It enables partial particle melting, which impacts pore defects in the denudation zone.more » Different pore formation mechanisms are observed at the edge of a scan track, at the melt pool bottom (during collapse of the pool depression), and at the end of the melt track (during laser power ramp down). Finally, we discuss remedies to these undesirable pores are discussed. The results are validated against the experiments and the sensitivity to laser absorptivity.« less

Comparison of bulk and pitcher-catcher targets for laser-driven neutron production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Willingale, L.; Maksimchuk, A.; Joglekar, A. S.

2011-08-15

Laser-driven d(d, n)-{sup 3}He beam-target fusion neutron production from bulk deuterated plastic (CD) targets is compared with a pitcher-catcher target scheme using an identical laser and detector arrangement. For laser intensities in the range of (1-3) x 10{sup 19} W cm{sup -2}, it was found that the bulk targets produced a high yield (5 x 10{sup 4} neutrons per steradian) beamed preferentially in the laser propagation direction. Numerical modeling shows the importance of considering the temperature adjusted stopping powers to correctly model the neutron production. The bulk CD targets have a high background target temperature leading to a reduced stoppingmore » power for the deuterons, which increases the probability of generating neutrons by fusion. Neutron production from the pitcher-catcher targets was not as efficient since it does not benefit from the reduced stopping power in the cold catcher target. Also, the inhibition of the deuteron acceleration by a proton rich contamination layer significantly reduces the pitcher-catcher neutron production.« less

Laser powder-bed fusion additive manufacturing: Physics of complex melt flow and formation mechanisms of pores, spatter, and denudation zones

DOE PAGES

Khairallah, Saad A.; Anderson, Andrew T.; Rubenchik, Alexander; ...

2016-02-23

Our study demonstrates the significant effect of the recoil pressure and Marangoni convection in laser powder bed fusion (L-PBF) of 316L stainless steel. A three-dimensional high fidelity powder-scale model reveals how the strong dynamical melt flow generates pore defects, material spattering (sparking), and denudation zones. The melt track is divided into three sections: a topological depression, a transition and a tail region, each being the location of specific physical effects. The inclusion of laser ray-tracing energy deposition in the powder-scale model improves over traditional volumetric energy deposition. It enables partial particle melting, which impacts pore defects in the denudation zone.more » Different pore formation mechanisms are observed at the edge of a scan track, at the melt pool bottom (during collapse of the pool depression), and at the end of the melt track (during laser power ramp down). Finally, we discuss remedies to these undesirable pores are discussed. The results are validated against the experiments and the sensitivity to laser absorptivity.« less

Twin-spot laser welding of advanced high-strength multiphase microstructure steel

NASA Astrophysics Data System (ADS)

Grajcar, Adam; Morawiec, Mateusz; Różański, Maciej; Stano, Sebastian

2017-07-01

The study addresses the results concerning the laser welding of TRIP (TRansformation Induced Plasticity) steel using a beam focused at two spots (also referred to as twin-spot laser welding). The analysis involved the effect of variable welding thermal cycles on the properties and microstructure of welded joints. The tests were performed using a linear energy of 0.048 and 0.060 kJ/mm and the laser beam power distribution of 50%:50%, 60%:40% and 70%:30%. The tests also involved welding performed using a linear energy of 0.150 kJ/mm and the laser beam power distribution of 70%:30%. In addition, the research included observations of the microstructure of the fusion zone, heat affected zone and the transition zone using light microscopy and scanning electron microscopy. The fusion zone was composed of blocky-lath martensite whereas the HAZ (heat-affected zone) was characterised by the lath microstructure containing martensite, bainite and retained austenite. The distribution of twin-spot laser beam power significantly affected the microstructure and hardness profiles of welded joints. The highest hardness (480-505 HV), regardless of welding variants used, was observed in the HAZ.

Numerical studies of the use of thin high-Z layers for reducing laser imprint in direct-drive inertial-fusion targets

NASA Astrophysics Data System (ADS)

Bates, Jason; Schmitt, Andrew; Karasik, Max; Obenschain, Steve

2012-10-01

Using the FAST code, we present numerical studies of the effect of thin metallic layers with high atomic number (high-Z) on the hydrodynamics of directly-driven inertial-confinement-fusion (ICF) targets. Previous experimental work on the NIKE Laser Facility at the U.S. Naval Research Laboratory demonstrated that the use of high-Z layers may be efficacious in reducing laser non-uniformities imprinted on the target during the start-up phase of the implosion. Such a reduction is highly desirable in a direct-drive ICF scenario because laser non-uniformities seed hydrodynamic instabilities that can amplify during the implosion process, prevent uniform compression and spoil high gain. One of the main objectives of the present work is to assess the utility of high-Z layers for achieving greater laser uniformity in polar-drive target designs planned for the National Ignition Facility. To address this problem, new numerical routines have recently been incorporated in the FAST code, including an improved radiation-transfer package and a three-dimensional ray-tracing algorithm. We will discuss these topics, and present initial simulation results for high-Z planar-target experiments planned on the NIKE Laser Facility later this year.

LIFE Materials: Overview of Fuels and Structural Materials Issues Volume 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farmer, J

2008-09-08

The National Ignition Facility (NIF) project, a laser-based Inertial Confinement Fusion (ICF) experiment designed to achieve thermonuclear fusion ignition and burn in the laboratory, is under construction at the Lawrence Livermore National Laboratory (LLNL) and will be completed in April of 2009. Experiments designed to accomplish the NIF's goal will commence in late FY2010 utilizing laser energies of 1 to 1.3 MJ. Fusion yields of the order of 10 to 20 MJ are expected soon thereafter. Laser initiated fusion-fission (LIFE) engines have now been designed to produce nuclear power from natural or depleted uranium without isotopic enrichment, and from spentmore » nuclear fuel from light water reactors without chemical separation into weapons-attractive actinide streams. A point-source of high-energy neutrons produced by laser-generated, thermonuclear fusion within a target is used to achieve ultra-deep burn-up of the fertile or fissile fuel in a sub-critical fission blanket. Fertile fuels including depleted uranium (DU), natural uranium (NatU), spent nuclear fuel (SNF), and thorium (Th) can be used. Fissile fuels such as low-enrichment uranium (LEU), excess weapons plutonium (WG-Pu), and excess highly-enriched uranium (HEU) may be used as well. Based upon preliminary analyses, it is believed that LIFE could help meet worldwide electricity needs in a safe and sustainable manner, while drastically shrinking the nation's and world's stockpile of spent nuclear fuel and excess weapons materials. LIFE takes advantage of the significant advances in laser-based inertial confinement fusion that are taking place at the NIF at LLNL where it is expected that thermonuclear ignition will be achieved in the 2010-2011 timeframe. Starting from as little as 300 to 500 MW of fusion power, a single LIFE engine will be able to generate 2000 to 3000 MWt in steady state for periods of years to decades, depending on the nuclear fuel and engine configuration. Because the fission blanket in a fusion-fission hybrid system is subcritical, a LIFE engine can burn any fertile or fissile nuclear material, including un-enriched natural or depleted U and SNF, and can extract a very high percentage of the energy content of its fuel resulting in greatly enhanced energy generation per metric ton of nuclear fuel, as well as nuclear waste forms with vastly reduced concentrations of long-lived actinides. LIFE engines could thus provide the ability to generate vast amounts of electricity while greatly reducing the actinide content of any existing or future nuclear waste and extending the availability of low cost nuclear fuels for several thousand years. LIFE also provides an attractive pathway for burning excess weapons Pu to over 99% FIMA (fission of initial metal atoms) without the need for fabricating or reprocessing mixed oxide fuels (MOX). Because of all of these advantages, LIFE engines offer a pathway toward sustainable and safe nuclear power that significantly mitigates nuclear proliferation concerns and minimizes nuclear waste. An important aspect of a LIFE engine is the fact that there is no need to extract the fission fuel from the fission blanket before it is burned to the desired final level. Except for fuel inspection and maintenance process times, the nuclear fuel is always within the core of the reactor and no weapons-attractive materials are available outside at any point in time. However, an important consideration when discussing proliferation concerns associated with any nuclear fuel cycle is the ease with which reactor fuel can be converted to weapons usable materials, not just when it is extracted as waste, but at any point in the fuel cycle. Although the nuclear fuel remains in the core of the engine until ultra deep actinide burn up is achieved, soon after start up of the engine, once the system breeds up to full power, several tons of fissile material is present in the fission blanket. However, this fissile material is widely dispersed in millions of fuel pebbles, which can be tagged as individual accountable items, and thus made difficult to divert in large quantities. Several topical reports are being prepared on the materials and processes required for the LIFE engine. Specific materials of interest include: (1) Baseline TRISO Fuel (TRISO); (2) Inert Matrix Fuel (IMF) & Other Alternative Solid Fuels; (3) Beryllium (Be) & Molten Lead Blankets (Pb/PbLi); (4) Molten Salt Coolants (FLIBE/FLiNaBe/FLiNaK); (5) Molten Salt Fuels (UF4 + FLIBE/FLiNaBe); (6) Cladding Materials for Fuel & Beryllium; (7) ODS FM Steel (ODS); (8) Solid First Wall (SFW); and (9) Solid-State Tritium Storage (Hydrides).« less

Development of two color laser diagnostics for the ITER poloidal polarimeter.

PubMed

Kawahata, K; Akiyama, T; Tanaka, K; Nakayama, K; Okajima, S

2010-10-01

Two color laser diagnostics using terahertz laser sources are under development for a high performance operation of the Large Helical Device and for future fusion devices such as ITER. So far, we have achieved high power laser oscillation lines simultaneously oscillating at 57.2 and 47.7 μm by using a twin optically pumped CH(3)OD laser, and confirmed the original function, compensation of mechanical vibration, of the two color laser interferometer. In this article, application of the two color laser diagnostics to the ITER poloidal polarimeter and recent hardware developments will be described.

Fusion policy advisory committee named

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

Department of Energy Secretary James Watkins has announced the formation of new Fusion Policy Advisory Committee which will recommend a policy for conducting DOE's fusion energy research program. Issues that will be considered by the committee include the balance of research activities within the programs, the timing of experiments to test the burning of plasma fuel, the International Thermonuclear Experimental Reactor, and the development of laser technologies, DOE said. Watkins said that he would be entirely open to the committee's advice.

Design of a normal incidence multilayer imaging x-ray microscope.

PubMed

Shealy, D L; Gabardi, D R; Hoover, R B; Walker, A B; Lindblom, J F; Barbee, T W

1989-01-01

Normal incidence multilayer Cassegrain x-ray telescopes were flown on the Stanford/MSFC Rocket X-Ray Spectroheliograph. These instruments produced high spatial resolution images of the Sun and conclusively demonstrated that doubly reflecting multilayer x-ray optical systems are feasible. The images indicated that aplanatic imaging soft x-ray /EUV microscopes should be achievable using multilayer optics technology. We have designed a doubly reflecting normal incidence multilayer imaging x-ray microscope based on the Schwarzschild configuration. The Schwarzschild microscope utilizes two spherical mirrors with concentric radii of curvature which are chosen such that the third-order spherical aberration and coma are minimized. We discuss the design of the microscope and the results of the optical system ray trace analysis which indicates that diffraction-limited performance with 600 Å spatial resolution should be obtainable over a 1 mm field of view at a wavelength of 100 Å. Fabrication of several imaging soft x-ray microscopes based upon these designs, for use in conjunction with x-ray telescopes and laser fusion research, is now in progress. High resolution aplanatic imaging x-ray microscopes using normal incidence multilayer x-ray mirrors should have many important applications in advanced x-ray astronomical instrumentation, x-ray lithography, biological, biomedical, metallurgical, and laser fusion research.

Simultaneous measurement of the HT and DT fusion burn histories in inertial fusion implosions

DOE PAGES

Zylstra, Alex B.; Herrmann, Hans W.; Kim, Yong Ho; ...

2017-05-23

Measuring the thermonuclear burn history is an important way to diagnose inertial fusion implosions. Here, using the gas Cherenkov detectors at the OMEGA laser facility, we measure the HT fusion burn in a H 2+T 2 gas-fueled implosion for the first time. Then, using multiple detectors with varied Cherenkov thresholds, we demonstrate a technique for simultaneously measuring both the HT and DT burn histories from an implosion where the total reaction yields are comparable. This new technique will be used to study material mixing and kinetic phenomena in implosions.

Simultaneous measurement of the HT and DT fusion burn histories in inertial fusion implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zylstra, Alex B.; Herrmann, Hans W.; Kim, Yong Ho

Measuring the thermonuclear burn history is an important way to diagnose inertial fusion implosions. Here, using the gas Cherenkov detectors at the OMEGA laser facility, we measure the HT fusion burn in a H 2+T 2 gas-fueled implosion for the first time. Then, using multiple detectors with varied Cherenkov thresholds, we demonstrate a technique for simultaneously measuring both the HT and DT burn histories from an implosion where the total reaction yields are comparable. This new technique will be used to study material mixing and kinetic phenomena in implosions.

Pulsed Power Design for a Small Repetitively Pulsed Electron Beam Pumped KrF Laser

DTIC Science & Technology

2003-06-01

fusion energy (IFE) requirements for rep-rate, efficiency, durability and cost. We have designed a pulsed power system for the pre-amplifier in the Electra...new advanced pulsed power topology that can meet the fusion energy requirements for durability, repetition rate, and cost. The pulsed power will first

Monte Carlo calculations of the incineration of plutonium and minor actinides of laser fusion inertial confinement fusion fission energy (LIFE) engine

NASA Astrophysics Data System (ADS)

Adem, ACIR; Eşref, BAYSAL

2018-07-01

In this paper, neutronic analysis in a laser fusion inertial confinement fusion fission energy (LIFE) engine fuelled plutonium and minor actinides using a MCNP codes was investigated. LIFE engine fuel zone contained 10 vol% TRISO particles and 90 vol% natural lithium coolant mixture. TRISO fuel compositions have Mod①: reactor grade plutonium (RG-Pu), Mod②: weapon grade plutonium (WG-Pu) and Mod③: minor actinides (MAs). Tritium breeding ratios (TBR) were computed as 1.52, 1.62 and 1.46 for Mod①, Mod② and Mod③, respectively. The operation period was computed as ∼21 years when the reference TBR > 1.05 for a self-sustained reactor for all investigated cases. Blanket energy multiplication values (M) were calculated as 4.18, 4.95 and 3.75 for Mod①, Mod② and Mod③, respectively. The burnup (BU) values were obtained as ∼1230, ∼1550 and ∼1060 GWd tM–1, respectively. As a result, the higher BU were provided with using TRISO particles for all cases in LIFE engine.

Technique Using Axicons For Generating Flat Top Laser Beam Profiles

NASA Astrophysics Data System (ADS)

Viswanathan, V. K.; Woodfin, G. L.; Stahl, D.; Carpenter, J. P.; Kyrala, G.

1983-11-01

In certain fusion experiments using CO2 lasers, like Helios, it is desired to produce a focal spot several times larger than the nominal focal spot, with a flat beam profile. The typical focal spot in Helios is roughly 70 μm and just defocussing the beam produces beam breakup, with several hot spots with roughly the original diameter, and a gaussian distribution. A number of schemes were tried to achieve a large spot with desired characteristics. These are described in the article. Axicons were found to produce spots with desired characteristics. Axicons are lenses or mirrors having a cone-shaped surface. The various schemes are described, as well as an. experiment in Helios which confirmed that axicons produced the spots with desirable characteristics. Helios is an 8-beam CO2 laser which produces 10 kJ at power in excess of 20 TW. It is currently being used for Laser Fusion studies at the Los Alamos National Laboratory.

Numerical simulation of spatter formation during fiber laser welding of 5083 aluminum alloy at full penetration condition

NASA Astrophysics Data System (ADS)

Wu, Dongsheng; Hua, Xueming; Huang, Lijin; Zhao, Jiang

2018-03-01

The droplet escape condition in laser welding is established in this paper. A three-dimensional numerical model is developed to study the weld pool convection and spatter formation at full penetration during the fiber laser welding of 5083 aluminum alloy. It is found that when laser power is 9 kW, the bottom of the keyhole is dynamically opened and closed. When the bottom of the keyhole is closed, the molten metal at the bottom of the back keyhole wall flows upwards along the fusion line. When the bottom of the keyhole is opened, few spatters can be seen around the keyhole at the top surface, two flow patterns exists in the rear part of the keyhole: a portion of molten metal flows upwards along the fusion line, other portion of molten metal flows to the bottom of the keyhole, which promote the spatter formation at the bottom of the keyhole rear wall.

FM-to-AM modulations induced by a weak residual reflection stack of sine-modulated pulses in inertial confinement fusion laser systems

NASA Astrophysics Data System (ADS)

Huang, Xiaoxia; Deng, Xuewei; Zhou, Wei; Hu, Dongxia; Guo, Huaiwen; Wang, Yuancheng; Zhao, Bowang; Zhong, Wei; Deng, Wu

2018-02-01

We report on frequency to amplitude modulation (FM-to-AM) conversion induced by a weak residual reflection stack of sine-modulated pulses in a complex laser system. Theoretical and experimental investigations reveal that when weak residual reflected pulses stack on the main pulse, the spectral intensity changes in the stacked region, which then converts to obvious AM. This kind of FM-to-AM effect often occurs in the tail of the pulse and cannot be eliminated by common compensation methods, which even enhance the modulation depth. Furthermore, the actual intensity modulation frequency and depth induced by the residual reflection stack are much higher and deeper than observed on the oscilloscope, which is harmful for safe operation of the laser facility and the driving power balance during inertial confinement fusion. To eliminate this kind of FM-to-AM effect, any possible on-axis and near-axis residual reflection in laser systems must be avoided.

Research of beam smoothing technologies using CPP, SSD, and PS

NASA Astrophysics Data System (ADS)

Zhang, Rui; Su, Jingqin; Hu, Dongxia; Li, Ping; Yuan, Haoyu; Zhou, Wei; Yuan, Qiang; Wang, Yuancheng; Tian, Xiaocheng; Xu, Dangpeng; Dong, Jun; Zhu, Qihua

2015-02-01

Precise physical experiments place strict requirements on target illumination uniformity in Inertial Confinement Fusion. To obtain a smoother focal spot and suppress transverse SBS in large aperture optics, Multi-FM smoothing by spectral dispersion (SSD) was studied combined with continuous phase plate (CPP) and polarization smoothing (PS). New ways of PS are being developed to improve the laser irradiation uniformity and solve LPI problems in indirect-drive laser fusion. The near field and far field properties of beams using polarization smoothing were studied and compared, including birefringent wedge and polarization control array. As more parameters can be manipulated in a combined beam smoothing scheme, quad beam smoothing was also studies. Simulation results indicate through adjusting dispersion directions of one-dimensional (1-D) SSD beams in a quad, two-dimensional SSD can be obtained. Experiments have been done on SG-III laser facility using CPP and Multi-FM SSD. The research provides some theoretical and experimental basis for the application of CPP, SSD and PS on high-power laser facilities.

Laser-driven magnetized liner inertial fusion

DOE PAGES

Davies, J. R.

2017-06-05

A laser-driven, magnetized liner inertial fusion (MagLIF) experiment is designed in this paper for the OMEGA Laser System by scaling down the Z point design to provide the first experimental data on MagLIF scaling. OMEGA delivers roughly 1000× less energy than Z, so target linear dimensions are reduced by factors of ~10. Magneto-inertial fusion electrical discharge system could provide an axial magnetic field of 10 T. Two-dimensional hydrocode modeling indicates that a single OMEGA beam can preheat the fuel to a mean temperature of ~200 eV, limited by mix caused by heat flow into the wall. One-dimensional magnetohydrodynamic (MHD) modelingmore » is used to determine the pulse duration and fuel density that optimize neutron yield at a fuel convergence ratio of roughly 25 or less, matching the Z point design, for a range of shell thicknesses. A relatively thinner shell, giving a higher implosion velocity, is required to give adequate fuel heating on OMEGA compared to Z because of the increase in thermal losses in smaller targets. Two-dimensional MHD modeling of the point design gives roughly a 50% reduction in compressed density, temperature, and magnetic field from 1-D because of end losses. Finally, scaling up the OMEGA point design to the MJ laser energy available on the National Ignition Facility gives a 500-fold increase in neutron yield in 1-D modeling.« less

Laser-driven magnetized liner inertial fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davies, J. R.

A laser-driven, magnetized liner inertial fusion (MagLIF) experiment is designed in this paper for the OMEGA Laser System by scaling down the Z point design to provide the first experimental data on MagLIF scaling. OMEGA delivers roughly 1000× less energy than Z, so target linear dimensions are reduced by factors of ~10. Magneto-inertial fusion electrical discharge system could provide an axial magnetic field of 10 T. Two-dimensional hydrocode modeling indicates that a single OMEGA beam can preheat the fuel to a mean temperature of ~200 eV, limited by mix caused by heat flow into the wall. One-dimensional magnetohydrodynamic (MHD) modelingmore » is used to determine the pulse duration and fuel density that optimize neutron yield at a fuel convergence ratio of roughly 25 or less, matching the Z point design, for a range of shell thicknesses. A relatively thinner shell, giving a higher implosion velocity, is required to give adequate fuel heating on OMEGA compared to Z because of the increase in thermal losses in smaller targets. Two-dimensional MHD modeling of the point design gives roughly a 50% reduction in compressed density, temperature, and magnetic field from 1-D because of end losses. Finally, scaling up the OMEGA point design to the MJ laser energy available on the National Ignition Facility gives a 500-fold increase in neutron yield in 1-D modeling.« less

Conceptual design of a laser fusion power plant. Part I. An integrated facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

This study is a new preliminary conceptual design and economic analysis of an inertial confinement fusion (ICF) power plant performed by Bechtel under the direction of Lawrence Livermore National Laboratory (LLNL). The purpose of a new conceptual design is to examine alternatives to the LLNL HYLIFE power plant and to incorporate information from the recent liquid metal cooled power plant conceptual design study (CDS) into the reactor system and balance of plant design. A key issue in the design of a laser fusion power plant is the degree of symmetry in the illumination of the target that will be requiredmore » for a proper burn. Because this matter is expected to remain unresolved for some time, another purpose of this study is to determine the effect of symmetry requirements on the total plant size, layout, and cost.« less

Exploring the limits of case-to-capsule ratio, pulse length, and picket energy for symmetric hohlraum drive on the National Ignition Facility Laser

NASA Astrophysics Data System (ADS)

Callahan, D. A.; Hurricane, O. A.; Ralph, J. E.; Thomas, C. A.; Baker, K. L.; Benedetti, L. R.; Berzak Hopkins, L. F.; Casey, D. T.; Chapman, T.; Czajka, C. E.; Dewald, E. L.; Divol, L.; Döppner, T.; Hinkel, D. E.; Hohenberger, M.; Jarrott, L. C.; Khan, S. F.; Kritcher, A. L.; Landen, O. L.; LePape, S.; MacLaren, S. A.; Masse, L. P.; Meezan, N. B.; Pak, A. E.; Salmonson, J. D.; Woods, D. T.; Izumi, N.; Ma, T.; Mariscal, D. A.; Nagel, S. R.; Kline, J. L.; Kyrala, G. A.; Loomis, E. N.; Yi, S. A.; Zylstra, A. B.; Batha, S. H.

2018-05-01

We present a data-based model for low mode asymmetry in low gas-fill hohlraum experiments on the National Ignition Facility {NIF [Moses et al., Fusion Sci. Technol. 69, 1 (2016)]} laser. This model is based on the hypothesis that the asymmetry in these low fill hohlraums is dominated by the hydrodynamics of the expanding, low density, high-Z (gold or uranium) "bubble," which occurs where the intense outer cone laser beams hit the high-Z hohlraum wall. We developed a simple model which states that the implosion symmetry becomes more oblate as the high-Z bubble size becomes large compared to the hohlraum radius or the capsule size becomes large compared to the hohlraum radius. This simple model captures the trends that we see in data that span much of the parameter space of interest for NIF ignition experiments. We are now using this model as a constraint on new designs for experiments on the NIF.

Nuclear science experiments with a bright neutron source from fusion reactions on the OMEGA Laser System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forrest, C. J.; Knauer, J. P.; Schroeder, W. U.

Subnanosecond impulses of 10 13 to 10 14 neutrons, produced in direct-drive laser inertial confinement fusion implosions, have been used to irradiate deuterated targets at the OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. The target compounds include heavy water (D 2O) and deuterated benzene (C 6D 6). Yields and energy spectra of neutrons from D(n,2n)p to study the breakup reaction have been measured at a forward angle of θlab = 3.5 degrees plus/minus 3.5 degrees with a sensitive, high-dynamic-range neutron time-of-flight spectrometer to infer the double-differential breakup cross section d2sigma/dEdomega for 14-MeV D–T fusionmore » neutrons.« less

Laser-driven fusion etching process

DOEpatents

Ashby, C.I.H.; Brannon, P.J.; Gerardo, J.B.

1987-08-25

The surfaces of solids are etched by a radiation-driven chemical reaction. The process involves exposing a substrate coated with a layer of a reactant material on its surface to radiation, e.g., a laser, to induce localized melting of the substrate which results in the occurrence of a fusion reaction between the substrate and coating material. The resultant reaction product and excess reactant salt are then removed from the surface of the substrate with a solvent which is relatively inert towards the substrate. The laser-driven chemical etching process is especially suitable for etching ionic substrates, e.g., LiNbO/sub 3/, such as used in electro-optical/acousto-optic devices. It is also suitable for applications wherein the etching process is required to produce an etched ionic substrate having a smooth surface morphology or when a very rapid etching rate is desired.

Hole Boring in a DT Pellet and Fast-Ion Ignition with Ultraintense Laser Pulses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Naumova, N.; Mourou, G.; Schlegel, T.

Recently achieved high intensities of short laser pulses open new prospects in their application to hole boring in inhomogeneous overdense plasmas and for ignition in precompressed DT fusion targets. A simple analytical model and numerical simulations demonstrate that pulses with intensities exceeding 10{sup 22} W/cm{sup 2} may penetrate deeply into the plasma as a result of efficient ponderomotive acceleration of ions in the forward direction. The penetration depth as big as hundreds of microns depends on the laser fluence, which has to exceed a few tens of GJ/cm{sup 2}. The fast ions, accelerated at the bottom of the channel withmore » an efficiency of more than 20%, show a high directionality and may heat the precompressed target core to fusion conditions.« less

Nuclear science experiments with a bright neutron source from fusion reactions on the OMEGA Laser System

DOE PAGES

Forrest, C. J.; Knauer, J. P.; Schroeder, W. U.; ...

2018-01-31

Subnanosecond impulses of 10 13 to 10 14 neutrons, produced in direct-drive laser inertial confinement fusion implosions, have been used to irradiate deuterated targets at the OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. The target compounds include heavy water (D 2O) and deuterated benzene (C 6D 6). Yields and energy spectra of neutrons from D(n,2n)p to study the breakup reaction have been measured at a forward angle of θlab = 3.5 degrees plus/minus 3.5 degrees with a sensitive, high-dynamic-range neutron time-of-flight spectrometer to infer the double-differential breakup cross section d2sigma/dEdomega for 14-MeV D–T fusionmore » neutrons.« less

Activation of theMercury Laser System: A Diode-Pumped Solid-State Laser Driver for Inertial Fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bayramian, A J; Beach, R J; Bibeau, C

Initial measurements are reported for the Mercury laser system, a scalable driver for rep-rated inertial fusion energy. The performance goals include 10% electrical efficiency at 10 Hz and 100 J with a 2-10 ns pulse length. We report on the first Yb:S-FAP crystals grown to sufficient size for fabricating full size (4 x 6 cm) amplifier slabs. The first of four 160 kW (peak power) diode arrays and pump delivery systems were completed and tested with the following results: 5.5% power droop over a 0.75 ms pulse, 3.95 nm spectral linewidth, far field divergence of 14.0 mrad and 149.5 mradmore » in the microlensed and unmicrolensed directions respectively, and 83% optical-to-optical transfer efficiency through the pump delivery system.« less

Time-resolved absolute measurements by electro-optic effect of giant electromagnetic pulses due to laser-plasma interaction in nanosecond regime

PubMed Central

Consoli, F.; De Angelis, R.; Duvillaret, L.; Andreoli, P. L.; Cipriani, M.; Cristofari, G.; Di Giorgio, G.; Ingenito, F.; Verona, C.

2016-01-01

We describe the first electro-optical absolute measurements of electromagnetic pulses (EMPs) generated by laser-plasma interaction in nanosecond regime. Laser intensities are inertial-confinement-fusion (ICF) relevant and wavelength is 1054 nm. These are the first direct EMP amplitude measurements with the detector rather close and in direct view of the plasma. A maximum field of 261 kV/m was measured, two orders of magnitude higher than previous measurements by conductive probes on nanosecond regime lasers with much higher energy. The analysis of measurements and of particle-in-cell simulations indicates that signals match the emission of charged particles detected in the same experiment, and suggests that anisotropic particle emission from target, X-ray photoionization and charge implantation on surfaces directly exposed to plasma, could be important EMP contributions. Significant information achieved on EMP features and sources is crucial for future plants of laser-plasma acceleration and inertial-confinement-fusion and for the use as effective plasma diagnostics. It also opens to remarkable applications of laser-plasma interaction as intense source of RF-microwaves for studies on materials and devices, EMP-radiation-hardening and electromagnetic compatibility. The demonstrated extreme effectivity of electric-fields detection in laser-plasma context by electro-optic effect, leads to great potential for characterization of laser-plasma interaction and generated Terahertz radiation. PMID:27301704

Time-resolved absolute measurements by electro-optic effect of giant electromagnetic pulses due to laser-plasma interaction in nanosecond regime

NASA Astrophysics Data System (ADS)

Consoli, F.; de Angelis, R.; Duvillaret, L.; Andreoli, P. L.; Cipriani, M.; Cristofari, G.; di Giorgio, G.; Ingenito, F.; Verona, C.

2016-06-01

We describe the first electro-optical absolute measurements of electromagnetic pulses (EMPs) generated by laser-plasma interaction in nanosecond regime. Laser intensities are inertial-confinement-fusion (ICF) relevant and wavelength is 1054 nm. These are the first direct EMP amplitude measurements with the detector rather close and in direct view of the plasma. A maximum field of 261 kV/m was measured, two orders of magnitude higher than previous measurements by conductive probes on nanosecond regime lasers with much higher energy. The analysis of measurements and of particle-in-cell simulations indicates that signals match the emission of charged particles detected in the same experiment, and suggests that anisotropic particle emission from target, X-ray photoionization and charge implantation on surfaces directly exposed to plasma, could be important EMP contributions. Significant information achieved on EMP features and sources is crucial for future plants of laser-plasma acceleration and inertial-confinement-fusion and for the use as effective plasma diagnostics. It also opens to remarkable applications of laser-plasma interaction as intense source of RF-microwaves for studies on materials and devices, EMP-radiation-hardening and electromagnetic compatibility. The demonstrated extreme effectivity of electric-fields detection in laser-plasma context by electro-optic effect, leads to great potential for characterization of laser-plasma interaction and generated Terahertz radiation.

Femtosecond laser-induced cell-cell surgical attachment.

PubMed

Katchinskiy, Nir; Godbout, Roseline; Goez, Helly R; Elezzabi, Abdulhakem Y

2014-04-01

Laser-induced cell-cell surgical attachment using femtosecond laser pulses is reported. We have demonstrated the ability to attach single cells using sub-10 femtosecond laser pulses, with 800 nm central wavelength delivered from a Ti:Sapphire laser. To check that the cells did not go through a cell-fusion process, a fluorescent dye Calcein AM was used to verify that the fluorescent dye did not migrate from a dyed cell to a non-dyed cell. The mechanical integrity of the attached joint was assessed using an optical tweezer. Attachment of cells was performed without the induction of cell-cell fusion, with attachment efficiency of 95%, and while preserving the cells' viability. Cell-cell attachment was achieved by delivery of one to two trains of femtosecond laser pulses lasting 15 ms each. Laser-induced ionization process led to an ultrafast reversible destabilization of the phospholipid layer of the cellular membrane. The inner cell membrane remained intact during the attachment procedure, and isolation of the cells' cytoplasm from the surrounding medium was obtained. A strong physical attachment between the cells was obtained due to the bonding of the membranes' ionized phospholipid molecules and the formation of a joint cellular membrane at the connection point. The cellular attachment technique, femtosecond laser-induced cell-cell surgical attachment, can potentially provide a platform for the creation of engineered tissue and cell cultures. © 2014 Wiley Periodicals, Inc.

Optical coatings on laser crystals for HiPER project

NASA Astrophysics Data System (ADS)

Oulehla, Jindrich; Pokorný, Pavel; Lazar, Josef

2011-06-01

In this contribution we present a technology for deposition of interference coatings for optical components designed to operate as active media in power pulsed lasers. The aim of the technology is to prepare crystals for lasers for the HiPER project (High Power laser Energy Research) which should demonstrate the feasibility of laser driven fusion as a future energy source. Diode pumped solid state lasers (DPSSL) are the most likely option for fusion ignition. The choice of material for the lasers active medium is critical. Some of the most important properties include the ability to be antireflection coated to reduce the energy losses and increase the overall efficiency. This contribution deals with some of the materials considered to be candidates for slabs serving as the active medium of the DPSSLs. We tested Yb:YAG, Yb:CaF2 and Yb:KGW samples. As large amounts of heat need to be dissipated during laser operation, cryogenic cooling is necessary. Appropriate coating materials and techniques need to be chosen. Therefore differences between available coating techniques are investigated in terms of adhesion, enduring of stress resulting from temperature shocks, etc. Coated samples were placed in a specially designed cryogenic apparatus in order to simulate conditions similar to those in real life operation. Optical microscopy and spectrophotometer measurements were used for coating investigation after the conducted experiments.